According to Newtons "First Law" what will happen if an astronauts security cable detaches?

Q.1 Why do bodies of small mass require small initial endeavor to bring them into move?
Answer: The inertia of a body is proportional to its mass. Smaller the mass, bottom is the opposition to the change of country of move.
Q.2 Tin can a body in linear motion be in equilibrium?
Answer: Yep, provided the vector sum of the forces acting upon the body is zero.
Q.3 A torso is acted upon past a number of external forces. Can it remain at remainder?

Answer: If the vector sum of all the external forces is aught, then the body will remain at rest.
Q.iv If the net strength acting on the trunk be goose egg, will the body remain necessarily in rest position?

Reply: No, the body may be in the state of uniform motility along a straight line even when the net forcefulness interim on the trunk is zero.
Q.v If a force is acting on a moving body perpendicular to the management of motion, then what volition be its effect on the speed and direction of the body?

Answer: There will be no change in the speed of the body simply the direction will change continuously.
Q.6 Why do the passengers fall in backward management when a bus suddenly starts moving from the rest position?
Answer: When the charabanc suddenly starts moving, the lower part of the passenger's body begins to move forth with the bus while the upper part tend to remain at rest due to inertia of rest.

Effect of Inertia

That is why a passenger standing or sitting loosely in a bus falls backward when the coach suddenly starts moving.
Q.7 Why are passengers thrown forrad from their seats when a speeding bus stops suddenly?

Respond: This is due to inertia of motion. When the speeding bus stops of a sudden, lower office of the body in contact with the seat stops. The upper part of the torso of the passengers tends to maintain its uniform move. Hence the passengers are thrown forrad.
Q.8 A man jumping out of a moving train falls with his caput forward. Why?
Reply: Equally the man jumps out from a moving train, his feet all of a sudden come to rest on touching the ground while the upper part of his trunk continues to move forrard. That is why he falls with his head forwards. In order to save himself, he should run through some distance in the forward direction.
Q.ix Why practice the blades of an electrical fan continue to rotate for some fourth dimension after the electric current is switched off?

Answer: This is due to inertia of motion that the blades of an electric fan continue to rotate for some time even after the fan has been switched off.
Q.10 A rock when thrown on a drinking glass window smashes the windowpane to pieces, but a bullet from the gun passes through making a clean hole. Why?
Answer: Due to its small-scale speed, the stone remains in contact with the windowpane for a longer duration. It transfers its motility to the pane and breaks it into pieces. Simply the particles of windowpane near the hole are unable to share the fast motion of the bullet and so remain undisturbed.
Q.xi We shell a blanket with stick to remove dust particles. Why?
Answer: When we trounce blanket with a stick, it comes into motion. But the dust particles proceed to be at residue due to inertia and get detached from the coating.
Q.12 If y'all jerk a piece of a paper placed under a book very quickly, the book will not move. Why?

Reply: The volume continues in its state of rest due to inertia.
Q.13 Why fruits fall down from a tree, when its branches are shaken?
Answer:  Earlier shaking the branches, fruits are at rest. When branches are shaken, they come in move while the fruits tend to remain at remainder due to inertia of rest. As a consequence fruits get detached from the branches and autumn down.
Q.xiv Why an athlete runs some steps before taking a jump?
Answer: An athlete always runs for some distance before taking a bound then that inertia of motion may help him in his muscular efforts to take a longer jump.
Q.fifteen A passenger sitting in a carriage at rest pushes it from inside. Will the carriage motion?

Respond: No, internal forces cannot produce motility in a system.
Q.16 If a ball is thrown up in a moving train, it comes back to the person'southward hands. Why?
Answer: Both during its upwards and downward move, the ball continues to move (inertia of motion) with the same horizontal Velocity as the train. In this period, the brawl covers the same horizontal distance as the train and so it comes back to the thrower's hands.
Q.17 Why are the passengers thrown out- wards when a auto in which they are travelling all of a sudden takes a circular turn?
Respond: This is because the passengers tend to maintain their direction of move (inertia of direction) while the direction of machine changes when information technology takes the turn.
Q.18 Why are the wheels of vehicles are provided with mudguards?

Answer: When the wheel rotates at a loftier speed, the mud sticking to the bicycle flies off tangentially, this is due to inertia of management. In order that the flying mud does not spoil the clothes of passersby, the wheels are provided with mudguards.
Q.19 An astronaut accidentally gets thrown out of his pocket-size spaceship accelerating in inter-stellar space at a constant rate of 100 ms⁻². What is the acceleration of the astronaut the instant afterwards he is outside the spaceship?

Answer: Bold that at that place are no nearby stars to exert gravitational force and the small spaceship exerts negligible gravitational force on the astronaut, then moment he gets out of the ship, there is no external force on him. By the beginning law of motion, the acceleration of the astronaut is zero.
Q.20 Why is Newton's kickoff police of movement also called constabulary of inertia?
Reply: Co-ordinate to Newton's start constabulary of movement, a body by itself cannot modify its state of remainder or of uniform in a directly line. This inability of a body is chosen inertia. That is why Newton'south first police of motion is besides chosen law of inertia.
Q.21 A thief jumps from the upper storey of a house with a load on his back. What is the forcefulness of the load on his back when the thief is in air

Reply: Zero. This is because a status of weight- lessness exists during a costless fall. W=yard(yard−a)=thou(g−m)=0.
Q.22 A soda-water bottle is falling freely. Will the bubbling of the gas rising in the h2o of the bottle?

Answer: Bubbles volition non rise in water. The h2o in the freely-falling bottle is in the state of weightlessness?  Consequently, the force per unit area in water does not increase with depth. No up thrust acts on the bubbles and they practice non rise.
Q.23 A bird is sitting on the floor of a wire cage and the cage is in the hand of a male child. The bird starts flying in the muzzle. Volition the boy experience any change in the weight of the cage?

Answer: The air inside the wire cage is in free contact with the atmospheric air. When the bird starts flight inside the cage, the weight of the bird is no more experienced and the cage will appear lighter than before.
Q.24 The distance travelled by a torso is directly proportional to time. Is any external force acting on information technology?
Answer:As s ∝ t or s=kt i.e., the body is moving with a compatible velocity and no external forcefulness is acting on. it.
Q.25 Chinawares are wrapped in straw newspaper before packing. Why?
Answer:The straw paper betwixt the chinaware increases the fourth dimension of experiencing the jerk during transportation. Hence, they strike confronting each other with less force and are less likely to exist damaged.
Q.26 Why we are injure less when we jump on a muddy floor in comparison to a hard flooring?

Answer: When nosotros jump on a muddy floor, the flooring is carried in the direction of the jump and the time interval Δt for which forcefulness acts is increased. This decreases rate of change of momentum and hence the forcefulness of reaction. Therefore we are injure less.
Q.27 Why are shockers used in cars, scooters and motorcycles?

Reply: In the result of jerk or jump, the time for which the strength lets increases. Since the product of strength and fourth dimension is to remain constant in a given situation, therefore the force decreases.
Q.28 Why buffers are provided between the bogies of a railway railroad train?

Answer: Due to buffer bound, the fourth dimension of touch on between the bogies increases, and the force acting between the bogies (F = Impulse / time) decreases. Consequently, passengers sitting inside the bogies do not experience stiff jerks. For the same reason shockers are provided in all vehicles.
Q.29 Why is it necessary to bend knees while jumping from greater pinnacle?

Answer: During the spring, our anxiety at once come to residuum and for this smaller time (F = Impulse / time) a large force acts on feet. If we curve the knees slowly, the value of time of impact increases and less force acts on our feet. So we get less hurt.
Q.thirty A brick can be pushed gently on the polish floor by applying force with our human foot. But if we kicking the brick, the foot is hurt. Why?
Answer: When the brick is kicked, the fourth dimension for which force is impressed is short and hence charge per unit of change of momentum of the brick is large. The brick in turn, due to reaction applies large forcefulness on the foot. This strength may injure our foot.
Q.31 Why is it that when a man jumps downwards from a height of several storey into a stretched tarpaulin, he receives no injury?

Answer: When the man jumps, the tarpaulin gets depressed at the place of touch. This increases the time of touch (Δt). As a result, the tarpaulin exerts a very minor forcefulness (F = impulse/time) on the human being, and he receives no injury.
Q.32 According to Newton's 3rd constabulary, every force is accompanied by equal and opposite force. How tin anything motility so?

Reply: Though action and reaction act simultaneously, simply they human action on unlike bodies. This makes the move possible.
Q.33 Why is information technology difficult to drive a nail into a wooden block without supporting information technology?

Answer: When nosotros hit the boom with a hammer, the nail and unsupported block together motion forwards equally an single organisation. At that place is no strength of reaction. When the block is rested against a support, the reaction of the back up holds y the block in position and the nail is driven into the cake.
Q.34 Why it is hard to climb up a greasy pole?

Respond: When a person climbs up a pole, he presses the pole downward with his anxiety and the pole, in turn, pushes the person upwards with an equal strength. If the pole  is greasy, its surface becomes slippery and the person is not able to printing it. As there is no activeness, there will be no reaction. Hence it becomes hard for the person to climb up.
Q.35 In a tug of state of war, the squad that pushes harder against the ground wins. Why?

Answer: The team that pushes harder against ground » gets greater reactional strength and this leads them to win.

Q.36 Tin can a sailboat be propelled past air blown at the sails from a fan attached to the boat?

Answer:No. When the fan pushes the sail by bravado air, the air too pushes the fan in the reverse direction. As the fan is as well a office of the boat, the vector sum of the momenta of the fan and the gunkhole is zero. The boat will move only if some external bureau applies forcefulness on it.
Q.37 A man is at remainder in the heart of a pond on perfectly frictionless ice. How tin he go himself to the shore?
Answer: If the man throws away his shirt in a direction contrary to the desired direction of move, he can get himself to the shore.
Q.38 Two bodies of masses K and thousand are allowed to autumn from the same height. If the air-resistance exist same for each body, will the two bodies reach the earth simultaneously?

Reply:No. Allow the air-resistance on each body exist F. Net downwardly force on torso of mass M = Mg - F Acceleration of body of mass Thousand, Similarly acceleration of body of mass m, a′

 Thus the acceleration of the larger mass is greater, information technology will attain the globe before.
Q.39 At that place is some water in a chalice placed on the pan of a spring balance. If we dip our finger in this water without touching the bottom of the chalice so what would be the effect on the reading of the balance?
Answer: The reading will increment. The h2o will exert up thrust on the finger and the finger will exert an equal force of reaction on water in the downwardly direction i.e., on the lesser of the beaker.
Q.40 Two boys having the same mass are standing on ice-skates at some distance autonomously on a friction- less surface. A rope is fastened around the body of a male child, the other cease of which is in the hand of the second boy. What would happen if the 2nd boy pulls the rope?
Answer: The two boys will move towards each other with the same velocity so that their combined momentum is nevertheless nothing (conservation of momentum).
Q.41 A retarding force is applied to stop a motor car. If the speed of the motor automobile is doubled, how much more than distance will it embrace before stopping nether the same retarding force?

Answer:  Work done against retarding strength =Loss in K.E. In starting time case,  ...(i)

 In second case,  ..(ii)

 From (i) and (2),   s′= 4s Thus the motor car volition embrace a altitude iv times longer than before.
Q.42 Why does a rifle give a backward kicking on firing a bullet?
Answer: Before firing, both the bullet and the rifle are at rest and their total momentum is zero. Afterwards firing, the bullet gains a large momentum in the frontward direction.  To conserve momentum, the rifle gains an equal momentum in the contrary direction. And so the rifle gives a backward kick.
Q.43 Why is it advisable to agree a gun tight to one's shoulder when information technology is beingness fired?
Respond: The recoiling gun can hurt the shoulder. If the gun is held tightly against the shoulder, the trunk and the gun will constitute one system. Total mass becomes large and the recoil velocity becomes small.
Q.44 When a body falls to the earth, the earth as well moves upwards to meet it. But the earth's motion is not noticeable. Why?
Answer: We know that acceleration is the ratio of applied strength and mass of the body. Since the earth is a massive body, therefore its dispatch is very small. Hence the move of the earth is not noticeable.
Q.45 A meteorite bums in the temper earlier it reaches the earth'southward surface. What happens to its momentum?
Respond: Since the meteorite moves nether the strength of gravity, therefore its momentum changes but remains conserved before and afterward burning.
Q.46 Why does a heavy rifle non kick as strongly as a calorie-free burglarize using the aforementioned cartridge?
Reply: Recoil velocity of a rifle,  Thus the recoil velocity of the heavy rifle is smaller than that of the light rifle, so it does non kick strongly.
Q.47 Why is static friction chosen a self adjusting force?
Answer:As the applied force increases, the static friction besides increases and becomes equal to the practical force. That is why static friction is called a cocky-adjusting force.
Q.48 Can nosotros get off a frictionless horizontal surface by jumping?

Answer: No, because a frictionless surface is unable to provide reaction which is necessary for jumping.
Q.49 Automobile tyres are generally provided with irregular projections over their surfaces. Why?

Answer: Irregular projections increase the friction between the safe tyres and the road. This provides a business firm grip between the tyres and the road and prevents slipping.
Q.fifty Carts with prophylactic tyres are easier to fly than those with fe wheels. Why?

Answer: The coefficient of friction betwixt rubber tyres and road is much smaller than that between atomic number 26 wheels and the route.

Q.51 Sand is thrown on tracks covered with snow. Why?
Answer: When tracks are covered with snowfall, in that location is considerable reduction of frictional force. Then, the driving is not safe. When sand is thrown on the snowfall-covered tracks, the frictional strength increases. Then, condom driving is possible.
Q.52 Why are wheels of automobiles made circular?

Answer: Circular wheels roll on the road and rolling friction comes into play during the motion of auto. Rolling friction is less than the sliding friction. It is due to this reason that wheels of automobiles are made circular.
Q.53 Proper aggrandizement of tyres of vehicles saves fuel. Why?
Reply:When the tyre is properly inflated, the surface area of contact between the tyre and the ground is reduced. This reduces rolling friction. Consequently, the machine- mobile covers greater distance for the aforementioned quantity of fuel consumed.
Q.54 It is difficult to move a cycle along a road with its brakes on. Explicate?
Answer: When the bike is moved with brakes on, the wheels tin only skid. And then, the friction is sliding in nature. Since the sliding friction is greater than rolling friction, therefore, information technology is difficult to motion a bicycle with its brakes on.
Q.55 A large size brake on bicycle is equally effective as small i. Comment.

Answer: Action of brakes is based upon friction. But the friction is independent of the area of surfaces in contact then long as the normal reaction remains the same. Hence, large size brakes and normal size trakes will be as effective if the material of brakes remains unchanged.
Q.56 Why is it difficult to put a cycle into motion than to maintain its motion?
Answer: To put a bike into motion, i needs to overcome limiting friction while to maintain its move, one needs to overcome kinetic friction. Limiting friction is greater than the kinetic friction. So it is difficult to put a cycle into move than to maintain its motion.
Q.57 How does friction assistance usa in walking?
Answer: Due to friction, nosotros are able to button the footing backward during walking. The reaction of the footing helps the states to motility forrad.
Q.58 Why do we slip on a rainy day?
Answer: On a rainy day, the moisture basis becomes very smooth. The friction between our anxiety and the ground is profoundly reduced. It causes us to slip.
Q.59 Why is it difficult to walk on sand?
Reply: Considering of its yielding nature, sand cannot exert as much forward thrust as difficult ground does.
Q.lx Why fictional force gets increased when a surface is polished beyond a sure limit?

Reply:When surfaces are highly polished, the area of contact betwixt them increases. As a result of this, a large number of atoms and molecules lying on both the surfaces start exerting strong attractive forces on each other and therefore frictional strength increases.
Q.61 When a person walks on a crude surface, the frictional force exerted by the surface on the person is opposite to direction of his movement. State whether information technology true or false?

Reply: False. When a person walks, he pushes the ground backward with his pes. The tendency of the foot when it is in the contact of the earth is to move astern. Hence the force of friction acts in the forward direction, i.eastward., in a management in which the man walks.
Q.62 Why has a equus caballus to pull a cart harder during the outset few steps of his movement? Or A horse has to apply more forcefulness to start a cart than to keep it moving. Why?

Respond: During the starting time few steps of his motion, the horse has to work against the limiting friction and once the cart starts moving, the horse has to work confronting kinetic friction which is less than limiting friction.
Q.63 Is it unreasonable to expect the coefficient of friction to exceed unity?

Answer:No. The coefficient is less than unity for normal plane surfaces. But when the surfaces are so irregular that they have sharp minute projections and cavities on them, then the coefficient of friction may exceed unity.
Q.64 Is friction a not-conservative force?

Answer: Yes. When the direction of move of a body reverses, the direction of friction is also reversed. Piece of work has 1 to exist washed against friction both during forrad and return journey i.e., work done confronting friction along a closed path is not nil. So friction is a non-conservative force.
Q.65 For uniform round motion, does the direction of centripetal force depend on the sense of rotation?

Answer: No. Whether a body revolves clockwise or anticlockwise, the centripetal force always acts along the radius towards the centre of the circle.
Q.66 A stone tied at the end of a string is whirled in a circumvolve. When the string breaks, the stoneflies abroad tangentially? Explicate why.
Answer:The instantaneous velocity of the stone moving circular the circle is along the tangent to the circular path. When the cord breaks, the centripetal force vanishes. Due to the inertia of motion, the stone flies away tangentially.
Q.67 Why does a child in a merry-go-round press the side of his seat radially outward?

Answer: In accordance with Newton's 3rd law, the seat will press the kid inward, providing the necessary centripetal force.
Q.68 Why does skidding takes place generally on a rainy 24-hour interval forth a curved path?
Answer: The force of friction between the road and the tyres of the vehicle may not be sufficient to provide the necessary centripetal force.
Q.69 A machine is taking a sudden turn to the left. A passenger in the front seat finds himself sliding towards the door. Explain, indicating the forces acting on the passenger and the car at this instant.
Respond: The passenger in the front seat slides towards the door i.e., away from the circular plough. This is considering of the centrifugal force acting on the passenger.
Q.70 The outer rails of a curved railway track is more often than not raised over the inner. Why?
Answer: When the outer rail of a curved railway rails is raised over the inner, the horizontal component of the normal reaction of the rails provides the necessary centripetal forcefulness for the train to enable it movement along the curved path.
Q.71 A motor cyclist is going in a vertical circle. What is the necessary condition so that he may non fall down?

Answer: The necessary status that the motor cyclist may not fall downwardly is mυ²/r≥ mg i.e., υ≥at the highest point and  at the everyman point.
Q.72 A saucepan containing h2o is rotated in a vertical circle. Explicate, why the water does not fall.
Respond:For its revolution in a vertical circle, water [n the bucket needs a centripetal force. The weight of the h2o due to which h2o tin fall is used up in providing the necessary centripetal forcefulness and the water does not fall.
Q.73 Why does a pilot looping a vertical loop lot fall down even at the highest point?

Answer: At the highest point of the vertical loop, the weight of the airplane pilot due to which he can fall is used up in providing him the necessary centripetal force.
Q.74 What is the maximum possible velocity at the lowest position for oscillation of a simple pendulum of length L. What can happen to the motion if the velocity exceeds this value?

Answer:The maximum possible velocity at the lowest point for oscillation of simple pendulum =  When velocity exceeds  but is less than the bob leaves the vertical circle. When υ=  the bob completes the vertical circumvolve.
Q.75 A cricket actor lowers his hands to catch the ball safely. Explain, why?
Answer: The impulse is equal to the production of the force exerted by the ball and the time of grab. By lowering the hands, the time of catch increases. Then the strength exerted on the hands becomes much smaller and it does not injure the cricketer.
Q.76  It is piece of cake to catch a table tennis ball than a cricket ball fifty-fifty both are moving with aforementioned velocity. Why?
Answer: Due to its small mass, the momentum of the table tennis brawl is much smaller than that of the cricket ball of same velocity. Less force is required to stop the table tennis ball than the cricket ball. Hence information technology is piece of cake to catch the table tennis ball than the cricket ball.
Q.77  Why does a cyclist bend inwards while riding forth a curved road?

Answer: A cyclist bends in because then the horizontal component of the normal reaction of the ground provides the necessary centripetal force for going forth the curved road.
Q.78 The motion of a particle of mass 1000 is described by y=ut+1/2gt²Find the force acting on the particle.

Respond: Nosotros take y=ut+1/2gtⁱⁱ Velocity,  Acceleration,

 F=ma=mg Thus the given equation describes the motion of a particle under acceleration due to gravity and y is the position coordinate in the direction of g.
Q.79 A particle of mass 0.3 kg is subjected to a force of F=−kx with k=15Nm^−one. What volition be its initial acceleration, if information technology is released from a indicate 20 cm abroad from the origin?
Answer: Here k=15Nm⁻¹, x=20cm=0.20m,m=0.3kg F=−kx=15×0.20=−3N Acceleration,     a
Q.80  block of mass M is pulled forth a horizontal frictionless surface past a rope of mass yard. A force P is practical at the free finish of the rope. Discover the force exerted by the rope on the cake.
Answer:If a is the acceleration produced, and so P=(M+one thousand)a   or a= Force exerted by the rope on the block F=Ma=
Q.81 Three forces F_ane,F₂and F₃ are interim on a particle of mass m, such that F2 and F₃ are mutually perpendicular and under their event, the particle remains stationary. What volition be the acceleration of the particle, if the strength F_ane is removed?
Respond:As the particle remains stationary nether the activeness of the three forces, so  When force  is removed, the net force left is  Acceleration, a=−
Q.82 A bound rest is attached to the ceiling of a elevator. A man hangs his purse on the spring and the spring reads 49 N, when the lift is stationary. What will be the reading of the spring residuum, if the lift moves downward with an acceleration of 5ms⁻ⁱⁱ.

Answer: When the lift is stationary. The reaction of the leap is equal to weight of the bag. ∴  R=mg=49N or m  When the lift moves downward. The reaction is R′=m(m−a)=5(ix.8−5)=24N.
Q.83 Why does Newton's starting time police force of move announced to be contradicted in our day-to-day life?

Answer: In our twenty-four hour period-to-day observations, nosotros detect that when we push a block lying on the surface of a tabular array, information technology covers some distance before it stops. At first sight, it seems to contradict Newton's first law of motion. However, the motility of the cake is being opposed by the force of friction between the block and the tabular array and as well by air resistance. In the absence of such opposing forces, the cake would continue to move on its own.
Q.84 Explicate, why (a) The passengers are thrown frontwards from their seats, when a speeding autobus stops of a sudden. (b) Does a cricketer movement his paw backwards while holding a catch? (c) Is the gunkhole pushed abroad when a man jumps out of the gunkhole?

Answer: (a) This is due to inertia of move. When the speeding double-decker stops of a sudden, lower part of the trunk in contact with the seat stops. The upper function of the body of the passengers tends to maintain its compatible move. Hence the passengers are thrown forward.

(b) When the ball is defenseless, the impulse received by the hands is equal to the product of the force exerted by the ball and the time taken to consummate the catch. By moving the hands backwards, the cricketer increases the fourth dimension of catch. The force exerted on his hands becomes much smaller and it does non injure him.

(c) Initially, the total momentum of the boat and the man is nix. As the human jumps out of the boat, he gains momentum in the forrard management. To conserve momentum, the boat also gains an equal and opposite momentum. So the boat moves away from the shore.
Q.85 Explain: (a) Why are brawl bearings used in machinery? (b) Why does a horse have to apply more force to commencement a cart than to keep information technology moving? (c) What is the need for cyberbanking the tracks?

Respond: (a) By using ball bearings between the moving parts of a machinery, the sliding friction gets converted into rolling friction. The rolling friction is much smaller than sliding friction. This reduces power dissipation.

(b) During the kickoff few steps of his motility, the horse has to work confronting the limiting friction and one time the cart starts moving, the horse has to work against kinetic friction which is less than limiting friction.

(c) When the circular track is banked, the horizontal component of the normal reaction of the road provides the necessary centripetal force for the vehicle to movement information technology along the curved path. This reduces clothing and tear of the tyres.
Q.86 The speed of driving a car safely depends upon the range of headlight. Explain.

Answer: By the range of the headlight of a car, nosotros mean the maximum altitude(due south) upwards to which an obstacle on the route can be seen past the driver in the darkness. The driver has to stop the car before it reaches the obstacle. The retarding forcefulness acting on the car is constant. If, on applying brakes, the retardation in the car is a, and then to stop the machine within distance s, the speed υ of the car should be less than. Thus the speed of the automobile depends on the range (southward) of the headlight.
Q.87 A bird is sitting on the floor of a closed glass cage and the muzzle is in the hand of a girl. Will the daughter experience whatsoever modify in the weight of the cage when the bird (i) starts flight in the muzzle with a constant velocity (ii) flies upwards with acceleration (iii) flies downward with acceleration?

Answer: In a closed cage, the inside air is bound with the cage.

(i) As the dispatch is zero, there is no change grand the weight of the cage.

(two) In this case, the reaction R is given by R−Mg=Ma or R=M(g+a) Thus the cage will appear heavier than before.

(iii) In this example, the reaction R is given past Mg−R=Ma or R=K(g−a) Thus the cage will appear lighter than before.
Q.88 A man stands in a lift going downward with uniform velocity. He experiences a loss of weight at the start but not when elevator is in compatible motion. Explain why?

Answer:The apparent weight is given by R=W−ma=mg−ma or R=thousand(1000−a) Since lift is in acceleration in the start, a≠0, so R<mg.When lift comes in uniform motion, dispatch ceases (a=0) and homo experiences his own weight.
Q.89 Aeroplanes having wings fly at low altitudes while jet planes fly at high altitudes. Why?
Answer: The wings of the aeroplane push the external air astern and the aeroplane moves forward by the reaction of the pushed air. At lower distance the air is dense and then the aeroplane receives sufficient reactional forcefulness to motion forward. In the jet plane the external air is sucked into the plane and compressed. Hence for the air to be dense is non only unnecessary but also undesirable. The reason is that jet planes wing with very large velocity. If air is dense, then due to the air-friction the plane will become very hot. Therefore, jet planes fly at high altitude where air-density is very small.
Q.ninety A person (mass m) is hanging from a rope fastened to a stationary airship (mass M). If the person climbs along the rope, then with what velocity the balloon will move and in what direction? The velocity of the person relative to the rope is υ.

Answer: The initial momentum of the person and airship is null. Hence when the person climbs, the airship volition come up down with such a velocity υ that the total momentum exist still goose egg. The velocity of the person dative to earth is (υ−u). Hence
grand(υ−u)−Mu=0 or u=
Q.91 A long rope is hanging, passing over a pulley. Two monkeys of equal weights climb upwards from the opposite ends of the rope. 1 of them climbs up more rapidly relative to rope. Which monkey will reach kickoff at the top? The caster is frictionless and the rope is massless and inextensible.
Answer:There is no external force which may provide momentum to whatever monkey. The monkeys themselves give equal momenta to each other (through the rope). Therefore, 2 monkeys will climb up the rope at the same charge per unit relative to the earth. Equally their masses are equal, they volition reach the top simultaneously.
Q.92 When a brawl is thrown upward, its momentum commencement increases so decreases. Is the conservation of momentum violated in this process?
Answer: No. The combined momentum of the ball and the world is conserved. The brawl attracts the earth by the same forcefulness every bit the earth attracts the brawl. When the ball moves upward, its momentum decreases in the upward direction but simultaneously the momentum of the globe increases in the upward direction at the aforementioned rate. Similarly, when the brawl falls down, its momentum increases in the downward direction but simultaneously the momentum of the earth increases in the upward direction at the aforementioned charge per unit.
Q.93 A disc of mass m is placed on a table. A stiff bound is attached to it and is vertical. To the other terminate of the spring is attached a disc of negligible mass.  What minimum forcefulness should exist practical to the upper disc to press the spring such that the lower disc is lifted off the table when the external force is suddenly removed?

Answer: The minimum applied forcefulness should be mg. When a force mg is applied vertically downwards on the upper disc, the lower disc gets pressed confronting the floor with a force equal to mg. The floors exerts an up reaction equal to mg. When the external force is all of a sudden removed, this forcefulness of reaction lifts up the lower disc.
Q.94 Can a single isolated force be in nature? Give reason.

Answer: No. According to Newton's third law of motion, to every action at that place is always an equal and opposite reaction. And so the forces always exist in pairs. When nosotros talk of a single force, we are but because only one aspect of the mutual interaction.
Q.95 A body is dropped from the ceiling of a transparent cabin falling freely towards the globe. Describe the motility of the body as observed past an observer (i) sitting in the cabin (2) standing on the earth.

Respond: (i) The body will appear stationary in air. (ii) The body will appear falling freely under gravity.
Q.96 A ball is suspended by a cord from the ceiling of a motor auto. What will exist the effect on the position of the brawl if (i) the car is moving with uniform velocity (ii) the car is moving with accelerated motion and (3) the car is turning towards right?
Reply: (i)The ball will remain suspended vertically. (ii) The ball will move in backward management. (iii) The ball will move towards left.
Q.97 When brakes are practical in a bicycle, the brake shoes use frictional force on the wheels. The forces are internal for the system (wheel). For retardation, external forces must human activity on the system. The force of friction at the route surface remains the aforementioned before and later on the brakes are applied(f=μR). How does the bicycle cease?
Respond: When brakes are practical, the wheels are prevented from rolling. During rolling, the friction at the road surface does not cause retardation. When rolling is prevented, the wheels have to slip on the road. The friction of the road at present causes retardation.
Q.98 A light cord passing over a smooth pulley connects ii blocks of masses m_ane and grand₂ (vertically). If the acceleration of the system is chiliad/8,observe the ratio of the two masses.
Answer:
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Source: https://edurev.in/studytube/Short--Long-Answer-Question--Part-1--Laws-of-Motio/b2193467-ecbe-4266-98f4-64d4c4d69b44_t

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