CBSE Class 11 Physics Laws of Motion MCQs Set B

Question: A roller coaster is designed such that riders experience “weightlessness” as they go round the top of a hill whose radius of curvature is 20 m. The speed of the car at the top of the hill is between
a) 16 m/s and 17 m/s
b) 13 m/s and 14 m/s
c) 14 m/s and 15 m/s
d) 15 m/s and 16 m/s
Answer: c

Question: A box is lying on an inclined plane what is the coefficient of static friction if the box starts sliding when an angle of inclination is 60°
a) 1.173
c) 2.732
b) 1.732
d) 1.677
Answer: b

Question: Physical independence of force is a consequence of
a) third law of motion
b) second law of motion
c) first law of motion
d) all of these laws
Answer: c

 Question:A uniform metal chain is placed on a rough table such that one end of it hangs down over the edge of the table. When one-third of its length hangs over the edge, the chain starts sliding. Then, the coefficient of static friction is
a) 3/4
b) 1/4
c) 2/3
d) 1/3
e) 1/2
Answer: e 

Question: A block has been placed on a inclined plane with the slope angle q, block slides down the plane at constant speed. The coefficient of kinetic friction is equal to
a) sinq
b) cosq
c) g
d) tanq
Answer: d

Question: A 5000 kg rocket is set for vertical firing. The exhaust speed is 800 m s^–1. To give an initial upward acceleration of 20 m s–2, the amount of gas ejected per second to supply the needed thrust will be (g = 10 m s^–2)
a) 185.5 kg s^–1 
b) 187.5 kg s^–1 
c) 127.5 kg s^–1 
d) 137.5 kg s^–1 
Answer: b

 Question: A shell, in flight, explodes into four unequal parts.
Which of the following is conserved?
a) Potential energy
b) Momentum
c) Kinetic energy
d) Both Potential energy and Kinetic energy
Answer: b

 Question: An ice cart of mass 60 kg rests on a horizontal snow path with coefficient of static friction 1/3 Assuming that there is no vertical acceleration, find the magnitude of the maximum horizontal force required to move the ice cart. (take, g = 9.Sms^-2)
a) lO0N
b) ll0N
c) 209N
d) l96N
Answer: d

Question: A 600 kg rocket is set for a vertical firing. If the exhaust speed is 1000 m s^–1, the mass of the gas ejected per second to supply the thrust needed to overcome the weight of rocket is
a) 117.6 kg s^–1 
b) 58.6 kgs^–1 
c) 6 kg s^–1 
d) 76.4 kg s^–1 
Answer: c

Question: A body of mass M hits normally a rigid wall with velocity V and bounces back with the same velocity. The impulse experienced by the body is
a) MV
b) 1.5MV
c) 2MV
d) zero
Answer: c

Question: If the force on a rocket, moving with a velocity of 300 m/s is 210 N, then the rate of combustion of the fuel is
a) 0.07 kg/s
b) 1.4 kg/s
c) 0.7 kg/s
d) 10.7 kg/s
Answer: c

Question: A bullet is fired from a gun. The force on the bullet is given by F = 600 – 2 × 105 t where, F is in newton and t in seconds. The force on the bullet becomes zero as soon as it leaves the barrel. What is the average impulse imparted to the bullet?
a) 9 Ns
b) zero
c) 1.8 Ns
d) 0.9 Ns
Answer: d

Question: A person holding a rifle (mass of person and rifle together is 100 kg) stands on a smooth surface and fires 10 shots horizontally, in 5 s. Each bullet has a mass of 10 g with a muzzle velocity of 800 m s^–1. The final velocity acquired by the person and the average force exerted on the person are
a) – 0.08 m s^–1 , 16 N
b) – 0.8 m s^–1 , 8 N
c) – 1.6 m s^–1 , 16 N
d) – 1.6 m s^–1 , 8 N
Answer: a

Question:A cart is sliding down a low friction incline. A device on the cart launches a ball, forcing the ball perpendicular to the incline, as shown above. Air resistance is negligible. Where will the ball land relative to the cart,?
a) Front of the cart
b) Back of the cart
c) Land in the cart
d) None of the options
Answer: c

Question: A conveyor belt is moving at a constant speed of 2 m s^–1. A box is gently dropped on it. The coefficient of friction between them is m = 0.5. The distance that the box will move relative to belt before coming to rest on it, taking g = 10 m s^–2, is
a) 0.4 m
b) 1.2 m
c) 0.6 m
d) zero
Answer: a

Question: A mass of 1 kg is thrown up with a velocity of 100 m/s. After 5 seconds, it explodes into two parts. One part of mass 400 g comes down with a velocity 25 m/s. The velocity of other part is (Take g = 10 m s^–2)
a) 40 m/s
b) 80 m/s
c) 100 m/s
d) 60 m/s
Answer: c

 Question: A ball of mass 0.25 kg attached to the end of a string of length 1.96 m is moving in a horizontal circle. The string will break if the tension is more than 25 N.What is the maximum speed with which the ball can be moved ?
a) 5 m/s
b) 3 m/s
c) 14 m/s
d) 3.92 m/s.
Answer: c

Question: A heavy uniform chain lies on horizontal table top.If the coefficient of friction between the chain and the table surface is 0.25, then the maximum fraction of the length of the chain that can hang over one edge of the table is
a) 20%
b) 25%
c) 35%
d) 15%
Answer: a

Question: Which one of the following statements is incorrect?
a) Rolling friction is smaller than sliding friction.
b) Limiting value of static friction is directly proportional to normal reaction.
c) Frictional force opposes the relative motion.
d) Coefficient of sliding friction has dimensions of length.
Answer: d

Question:The force required to move a body up a rough inclined plane is double the force required to prevent the body from sliding down the plane. The coefficient of friction, when the angle of inclination of the plane is 60 ° is 
a) 1/3
b) 1/✓2
c) (1/✓3)
d) (1/2)
Answer: c

 Question: A stone is dropped from a height h. It hits the ground with a certain momentum P. If the same stone is dropped from a height 100% more than the previous height, the momentum when it hits the ground will change by
a) 68%
b) 41%
c) 200%
d) 100%
Answer: b

Question:A sphere rolls down an inclined plane of inclination 0. What is the acceleration as the sphere reaches bottom?
a) 5/7 g sin θ
b) 3/5 g sin θ
c) 2/7 g sin θ
d) 2/7 g sin θ
Answer: a

Question: A block moving on a surface with velocity 20 ms^-1, comes to rest because of surface friction over a distance of 40 m. The coefficient of dynamic function is ( take, g = 10 m s ^-2)
a) 0.5
b) 0.3
c) 0.2
d) 0.1
Answer: a

Question: To determine the coefficient of friction between a rough surface and a block, the surface is kept inclined at 45° and the block is released from rest. The block takes a time t in moving a distanced. The rough surface is then replaced by a smooth surface and the same experiment is repeated. The block now takes a time t/2 in moving down the same distance d. The coefficient of friction is
a) 3/4
b) 5/4
c) 1/2
d) 1/✓3
Answer: a

Question: A block of mass 10 kg placed on rough horizontal surface having coefficient of friction m = 0.5, if a horizontal force of 100 N acting on it then acceleration of the block will be
a) 10 m/s²
b) 5 m/s²
c) 15 m/s²
d) 0.5 m/s²
Answer: b

Question: A 10 N force is applied on a body produce in it an acceleration of 1 m/s². The mass of the body is
a) 15 kg
b) 20 kg
c) 10 kg
d) 5 kg
Answer: c

Question: In a rocket, fuel burns at the rate of 1 kg/s. This fuel is ejected from the rocket with a velocity of 60 km/s. This exerts a force on the rocket equal to 
a) 6000 N
b) 60000 N
c) 60 N
d) 600 N
Answer: b

Question: On the horizontal surface of a truck a block of mass 1 kg is placed (m = 0.6) and truck is moving with acceleration 5 m/s2 then the frictional force on the block will be
a) 5 N
b) 6 N
c) 5.88 N
d) 8 N
Answer: a

 Question: A man fires a bullet of mass 200 g at a speed of 5 m/s. The gun is of one kg mass. By what velocity the gun rebounds backward?
a) 1 m/s
b) 0.01 m/s
c) 0.1 m/s
d) 10 m/s.
Answer: a

Question: Consider a car moving along a straight horizontal road with a speed of 72 km/h. If the coefficient of static friction between the tyres and the road is 0.5, the shortest distance in which the car can be stopped is (taking g = 10 m/s²)
a) 30 m
b) 40 m
c) 72 m
d) 20 m
Answer: b