Students can refer to the following **MCQ Questions for Class 11 Laws of Motion** with Answers provided below based on the latest curriculum and examination pattern issued by CBSE and NCERT. Our teachers have provided here collection of multiple choice questions for Chapter 5 Laws of Motion Class 11 Physics covering all topics in your textbook so that students can assess themselves on all important topics and thoroughly prepare for their exams

## Laws of Motion Class 11 Physics MCQ Questions with Answers

We have provided below MCQs questions for Class 11 Laws of Motion with answers which will help the students to go through the entire syllabus and practice multiple choice questions provided here with solutions. As MCQ Questions for Class 11 Physics pdf download can be really scoring for students, you should go through all problems provided below so that you are able to get more marks in your exams.

#### MCQ Questions for Class 11 Laws of Motion

**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 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. Sand is being dropped on a conveyer belt at the rate of M kg/s. The force necessary to keep the belt moving with a constant velocity of v m/s will be **

(a) Mv /2 newton

(b) zero

(c) Mv newton

(d) 2 Mv newton

**Answer**

C

**Question. A cricketer catches a ball of mass 150 gm in 0.1 sec moving with speed 20 m/s, then he experiences force of **

(a) 300 N

(b) 30 N

(c) 3 N

(d) 0.3 N

**Answer**

B

**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 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 force of 6 N acts on a body at rest and of mass 1 kg. During this time, the body attains a velocity of 30 m/s. The time for which the force acts on the body is **

(a) 7 seconds

(b) 5 seconds

(c) 10 seconds

(d) 8 seconds

**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. 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 kg s–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. A 0.5 kg ball moving with a speed of 12 m/s strikes a hard wall at an angle of 30° with the wall. It is reflected with the same speed at the same angle. If the ball is in contact with the wall for 0.25 seconds, the average force acting on the wall is **

(a) 96 N

(b) 48 N

(c) 24 N

(d) 12 N

**Answer**

C

**Question. An explosion breaks a rock into three parts in a horizontal plane. Two of them go off at right angles to each other. The first part of mass 1 kg moves with a speed of 12 m s ^{–1 }and the second part of mass 2 kg moves with 8 m s–1 speed. If the third part flies off with 4 m s^{–1} speed, then its mass is **

(a) 7 kg

(b) 17 kg

(c) 3 kg

(d) 5 kg

**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. An explosion blows a rock into three parts. Two parts go off at right angles to each other. These two are, 1 kg first part moving with a velocity of 12 m s ^{–1} and 2 kg second part moving with a velocity 8 m s^{–1}. If the third part flies off with a velocity of 4 m s^{–1}, its mass would be **

(a) 7 kg

(b) 17 kg

(c) 3 kg

(d) 5 kg

**Answer**

D

**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 shell, in flight, explodes into four unequal parts. **

Which of the following is conserved?

(a) Potential energy

(b) Momentum

(c) Kinetic energy

(d) Both (a) and (c).

**Answer**

B

**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. A body of mass 5 kg explodes at rest into three fragments with masses in the ratio 1 : 1 : 3. The fragments with equal masses fly in mutually perpendicular directions with speeds of 21 m/s. The velocity of heaviest fragment in m/s will be **

(a) 7 2

(b) 5 2

(c) 3 2

(d) 2

**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. 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 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. 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 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. 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

**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. Starting from rest, a body slides down a 45° inclined plane in twice the time it takes to slide down the same distance in the absence of friction. The coefficient of friction between the body and the inclined plane is **

(a) 0.80

(b) 0.75

(c) 0.25

(d) 0.33

**Answer**

D

**Question. A block of mass 10 kg is in contact against the inner wall of a hollow cylindrical drum of radius 1 m. ****The coefficient of friction between the block and the inner wall of the cylinder is 0.1. The minimum angular velocity needed for the cylinder to keep the block stationary when the cylinder is vertical and rotating about its axis, will be (g = 10 m/s2)**(a) 10 p rad/s

(b) 10 rad/s

(c) 10 /2π rad/s

(d) 10 rad/s

**Answer**

D

**Question. Two stones of masses m and 2m are whirled in horizontal circles, the heavier one in a radius r/2 and the lighter one in radius r. The tangential speed of lighter stone is n times that of the value of heavier stone when they experience same centripetal forces. **

The value of n is

(a) 4

(b) 1

(c) 2

(d) 3

**Answer**

C

**Question. A car is moving in a circular horizontal track of radius 10 m with a constant speed of 10 m/s. A bob is suspended from the roof of the car by a light wire of length 1.0 m. The angle made by the wire with the vertical is **

(a) p/3

(b) p/6

(c) p/4

(d) 0°

**Answer**

C

**Question. A car of mass 1000 kg negotiates a banked curve of radius 90 m on a frictionless road. If the banking angle is 45°, the speed of the car is **

(a) 20 m s–1

(b) 30 m s–1

(c) 5 m s–1

(d) 10 m s–1

**Answer**

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 500 kg car takes a round turn of radius 50 m with a velocity of 36 km/hr. The centripetal force is **

(a) 1000 N

(b) 750 N

(c) 250 N

(d) 1200 N

**Answer**

A

**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. When milk is churned, cream gets separated due to **

(a) centripetal force

(b) centrifugal force

(c) fricitional force

(d) gravitational force

**Answer**

B

**Question. Three blocks with masses m, 2m and 3m are connected by strings, as shown in the figure. After an upward force F is applied on block m, the masses move upward at constant speed v. What is the net force on the block of mass 2m? (g is the acceleration due to gravity) **

(a) 3mg

(b) 6mg

(c) zero

(d) 2mg

**Answer**

C

**Question. A person of mass 60 kg is inside a lift of mass 940 kg and presses the button on control panel. The lift starts moving upwards with an acceleration 1.0 m/s2. If g = 10 m s–2, the tension in the supporting cable is **

(a) 8600 N

(b) 9680 N

(c) 11000 N

(d) 1200 N

**Answer**

C

**Question. The mass of a lift is 2000 kg. When the tension in the supporting cable is 28000 N, then its acceleration is **

(a) 4 m s–2 upwards

(b) 4 m s–2 downwards

(c) 14 m s–2 upwards

(d) 30 m s–2 downwards

**Answer**

A

**Question. A block of mass m is placed on a smooth wedge of inclination q. The whole system is accelerated horizontally so that the block does not slip on the wedge. The force exerted by the wedge on the block will be (g is acceleration due to gravity) **

(a) mg cosq

(b) mg sinq

(c) mg

(d) mg/cosq

**Answer**

D

**Question. A man weighs 80 kg. He stands on a weighing scale in a lift which is moving upwards with a uniform acceleration of 5 m/s2. What would be the reading on the scale ? (g = 10 m/s2) **

(a) zero

(b) 400 N

(c) 800 N

(d) 1200 N

**Answer**

D

**Question. A monkey of mass 20 kg is holding a vertical rope. The rope will not break when a mass of 25 kg is suspended from it but will break if the mass exceeds 25 kg. What is the maximum acceleration with which the monkey can climb up along the rope? **

(g = 10 m/s2)

(a) 5 m/s2

(b) 10 m/s2

(c) 25 m/s2

(d) 2.5 m/s2

**Answer**

D

**Question. A lift of mass 1000 kg which is moving with acceleration of 1 m/s2 in upward direction, then the tension developed in string which is connected to lift is **

(a) 9800 N

(b) 10,800 N

(c) 11,000 N

(d) 10,000 N

**Answer**

B

**Question. A mass of 1 kg is suspended by a thread. It is (i) lifted up with an acceleration 4.9 m/s2, (ii) lowered with an acceleration 4.9 m/s2. **

The ratio of the tensions is

(a) 1 : 3

(b) 1 : 2

(c) 3 : 1

(d) 2 : 1

**Answer**

C

**Question. A monkey is decending from the branch of a tree with constant acceleration. If the breaking strength of branch is 75% of the weight of the monkey, the minimum acceleration with which monkey can slide down without breaking the branch is **

(b) 3g/4

(c) g/4

(d) g/2

**Answer**

C

**Question.****The resultant of two forces acting at an angle of I 20° is 10 kg-wt and is perpendicular to one of the forces. That force is**

(a) 10/✓3kg-wt

(b) I0kg – wt

(c) 20✓3 kg-wt

(d) 10✓3 kg-wt

**Answer**

A

**Question.****An object is kept on a smooth inclined plane of 1 in /. The horizontal acceleration to be imparted to the inclined plane so that the object is stationary relative to the inclined is**

**Answer**

C

**Question.****A piece of wire is bent in the shape of a parabola y = kx ^{2} (y-axis vertical) with a bead of mass m on it. The bead can slide on the wire without friction. It stays at the lowest point of the parabola when the wire is at rest. The wire is now accelerated parallel to the x-axis with a constant acceleration a. The distance of the new equilibrium position of the bead, where the bead can stays at rest with respect to the wire, from the y -axis is**(

a) a/g k

(b) a/2gk

(c) 2a/gk

(d) a/4gk

**Answer**

B

**Question.****Two particles of equal mass are connected to a rope AB of negligible mass, such that one is at end A and the other dividing the length of the rope in the ratio 1 : 2 from B. The rope is rotated about end B in a horizontal plane. Ratio of the tensions in the smaller pa1t to the other is (ignore effect of gravity)**

(a) 4 : 3

(b) l : 4

(c) 1 : 2

(d) 1 : 3

**Answer**

D

**Question.** A steel wire can withstand a load upto 2940 N. A load of 150 kg is suspended from a rigid support. The maximum angle through which the wire can be displaced from the mean position, so that the wire does not break when the load passes through the position of equilibrium, is

(a) 30°

(b) 60°

(c) 80°

(d) 85

**Answer**

B

**Question.****A body of weight 2 kg is suspended as shown in figure. The tension T _{1 }in the horizontal string (in kg-wt) is**

(a) 2✓3

(b) ✓3/2

(c) ✓3

(d) 2

**Answer**

A

**Question.****If a street light of mass M is suspended from the end of a uniform rod of length L in different possible patterns as shown in figure, then**

(a) pattern A is more sturdy

(b) pattern B is more sturdy

( c) pattern C is more sturdy

(d) All will have same sturdiness

**Answer**

A

**Question.****The adjacent figure is the part of a horizontally stretched net. Section AB is stretched with a force of 10 N. The tensions in the sections BC and BF are**

(a) 10N, 11 N

(b) 10N, 6N

(c) ION, JON

(d) Can’t be calculated due to insufficient data

**Answer**

C

**Question.** A mass M kg is suspended by a weightless string. The horizontal force required to hold the mass at 60° with the vertical is

**Answer**

B

**Question.****Block A of mass 2 kg is placed over block B of mass 8 kg. The combination is placed over a rough horizontal surface. Coefficient of friction between B and the floor is 0.5. Coefficient of friction between A and Bis 0.4. A horizontal force of 10 N is applied on block B. The force of friction between A and B is**

(a) zero

(c) 40N

(b) SON

(d) IOON

**Answer**

B

**Question.****An object is gently placed on a long converges belt moving with l l ms ^{-1 .}If the coefficient of friction is 0.4, then the block will slide in the belt upto a distance of**

(a) 10.21 m

(b) 15.125 m

(c) 20.3m

(d) 25.6 m

**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.** Three blocks of masses m_{1}, m_{2} and m_{3} are connected by massless string as shown kept on a frictionless table.

**They are pulled with a force T _{3} = 40 N. If m_{1} = IO kg, m_{2 }= 6 kg and m_{3} = 4 kg, the tension T_{2} will be**

(a) 20 N

(c) 40 N

(c)l ON

(d) 32 N

**Answer**

D

**Question.****A block of mass 0.18 kg is attached to a spring of force constant 2 NI m . The coefficient of friction between the block and the floor is 0.1. Initially the block is at rest and the spring is unstretched. An impulse is given to the block. The block slides a distance of0.06 m and comes to rest for the first time the initial velocity of the block in mis is v= N I 10. Then, N is**

(a) 2

(b) 3

(c) 4

(d) 6

**Answer**

C

**Question.** A box of mass 2 kg is placed on the roof of a car. The box would remain stationary until the car attains a maximum acceleration. Coefficient of static friction between the box and the roof of the car is 0.2 and g = 10 ms-2 The maximum acceleration of the car, for the box to remain**stationary, is **

(a) 8 ms^{-2}

(b) 6 ms^{-2}

(c) 4 m^{-2}

(d) 2 ms^{-2}

**Answer**

**Question.****Two masses m _{1} = I kg and m_{2} = 2 kg are connected by a light inextensible string and suspended by means of a weightless pulley as shown in the figure.**

Assuming that both the masses start from rest, the distance travelled by the centre of mass in 2 s is (take, g = lOm/s^{2})

**Answer**

A

**Question.****Two masses 8 kg and 12 kg are connected at the two ends of a string that goes over a frictionless pulley. Calculate the acceleration of the masses and the tension in the string. (take, g = 10m/s ^{2})**

(a) 8m/s

^{2 },144N

(b) 4m/s

^{2 },112N

(c) 6m/s

^{2}, 128N

(d) 2m/s

^{2},96N

**Answer**

D

**Question.****Three blocks of masses 4 kg, 2 kg and 1 kg respectively are in contact on a frictionless table as shown in the figure. If a force of 14 N is applied on the 4 kg block, the contact force between the 4 kg and the 2 kg block will be**

(a) 2 N

(b) 6 N

(c) 8 N

(d) 14 N

**Answer**

B

**Question.****The backside of a truck is open and a box of 40 kg is placed 5 m away from the rear end. The coefficient of friction of the box with the surface of the truck is 0.15. The truck starts from rest with 2 m/s ^{2} acceleration. Calculate the distance covered by the truck when the box falls off.**

(a) 20m

(b) 30m

(c) 40m

(d) 50m

**Answer**

A

**Question.****The engine of a car produces an acceleration of 6 ms ^{-2} in the car. If this car pulls another car of the same mass, then the acceleration would be**

(a) 6ms

^{-2}

(b) 12ms

^{-2}

(c) 3ms

^{-2}

(d) l.5ms

^{-2}

**Answer**

C

**Question.** A block A weighing 100 kg rests on a block B and is tied with a horizontal string to the wall at C. Block B weighs 200 kg. The coefficient of friction between A and Bis 0.25 and between B and the surface is l /3. The horizontal force P necessary to move the block B should be (take, g = 10m/s^{2})

(a) l150N

(b) 1250N

(c) 1300N

(d) 1420N

**Answer**

B

**Question.****A block of mass 2 kg is at rest on a floor. The coefficient of static friction between block and the floor is 0.54. A horizontal force of 2.8 N is applied to the block. What should be the frictional force between the block and the floor? (take,g = 10 m/s ^{2})**

(a) 8.8N

(b) 5.8N

(c) 2.8N

(d) JO.SN

**Answer**

C

**Question.** A block of mass M placed on a frictionless horizontal table is pulled by an other block of mass m hanging vertically by a massless string passing over a frictionless pulley. The tension in the string is

**Answer**

D

**Question.** Starting from rest, the time taken by a body sliding down on a rough inclined plane at45° with the horizontal is twice the time taken to travel on a smooth plane of same inclination and same distance. Then, the coefficient of kinetic friction is

(a) 0.25

(b) 0.33

(c) 0.50

(d) 0.75

**Answer**

D

**Question.****Block A of mass m and block B of mass 2m are placed on a fixed triangular wedge by means of a massless, inextensible string and a frictionless pulley as shown in figure. The wedge is inclined at 45° to the horizontal on both the sides. The coefficient of friction between the block A and the wedge is 2/3 and that between the block B and the wedge is 1/3 and both the blocks A and B are released from rest, the acceleration of A will be**

(a) -1

(b) 1.2

(c) 0.2

(d) zero

**Answer**

D

**Question.****In the figure shown, m _{1} = IO kg, m_{2} = 6 kg, m_{3} = 4 kg. If T_{3} = 40N, T_{2} = ?**

(a) 13 N

(b) 32 N

(c) 25 N

(d) 35 N

**Answer**

B

**Question.****The coefficient of limiting friction μ is defined as**

**Answer**

C

**Question.****A marble block of mass 2 kg lying on ice when given a velocity of 6 ms ^{-1} is stopped by friction in 10 s. Then, the coefficient of friction is**

(a) 0.02

(b) 0.03

(c) 0.06

(d) 0.01

**Answer**

C

**Question.** Two masses M and M/2 are joined together by means of light inextensible string passed over a frictionless pulley as shown in the figure. When the bigger mass is released, the small one will ascend with an acceleration of

(a) I

(b) 3g/32

(c) I

(d) g

**Answer**

A

**Question.** The pulleys and strings shown in the figure are smooth and of negligible mass. For the system to remain in equilibrium, the angle 0 should be

(a) 0°

(c) 45°

(b) 30°

(d) 60°

**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 B is pushed momentarily along a horizontal surface with an initial velocity v. If μ is the coefficient of sliding friction between B and the surface, block B will come to rest after a time**

(a) v/gμ

(b) gμ/V

(c) g/V

(d) V/g

**Answer**

A

**Question.** In the arrangement shown in figure, the strings are light and inextensible. The surface over which blocks are placed is smooth. What is the acceleration of each block?

(a) 8 ms^{-2}

(b) 4 ms^{-2}

(c) 2 ms^{-2}

(d) 14 rns^{-2}

**Answer**

B

**Question.****The tension in the string in the pulley system shown in the figure is**

(a) 75 N

(b) 80 N

(c) 7.5 N

(d) 30 N

**Answer**

A

**Question.****Two blocks of masses 1 kg and 2 kg are com1ected by a metal wire going over a smooth pulley as shown in figure. The breaking stress of the metal is 2 x 10 ^{9} Nm – z. What should be the minimum radius of the wire used if it is not to break? (take, g = lOms^{-2})**

(a) 4.6x l0^{-5} m

(c) 2.5 X 10^{-6} m

(b) 4.6 x 10^{-6} m

(d) 2.5 X 10^{-5} m

**Answer**

A

**Question.****A block of mass 2 kg rests on a horizontal surface. If a horizontal force of 5 N is applied on the block, the frictional force on it is (take,μ k = 0.4, μ s = 0.5)**

(a) 5 N

(b) 10 N

(c) 8 N

(d) zero

**Answer**

C

**Question.****A body is coming with a velocity of 72 kmh ^{-1 }on a rough horizontal surface of coefficient of friction 0.5. If the acceleration due to gravity is 10 ms ^{-2}, find the minimum distance, it can be stopped.**

(a) 400 rn

(b) 40 m

(c) 0.40 rn

(d) 4 m

**Answer**

B

**Question.** In the given figure, the pulley is assumed massless and frictionless. If the friction force on the object of mass m is f, then its acceleration in terms of the force F will be equal to

**Answer**

D

**31. 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.****Two masses A and B of 15 kg and 10 kg are connected with a string passing over a frictionless pulley fixed at the corner of a table (as shown in figure). The coefficient of friction between the table and block is 0.4. The minimum mass of C, that may be placed on A to prevent it from moving is**

(a) 10 kg

(b) 5 kg

(c) zero

(d) 15 kg

**Answer**

A

**Question.****Two masses m _{1} and m_{2} (m_{1} > m_{2} ) are connected by massless flexible and inextensible string passed over massless and frictionless pulley. The acceleration of centre of mass is**

**Answer**

A

**Question.****A block of mass m is placed on a surface with a vertical cross-section given by y = x ^{3} I 6. If the coefficient of friction is 0.5, the maximum height above the ground at which the block can be placed without slipping is. **(a) (1/6) m

(b) (2/3) m

(c) (1/3) m

(d) (1/2) m

**Answer**

A

**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.****Two blocks of masses M and m are connected by a string passing over a pulley as shown in the figure. The downward acceleration of the block with mass m is**

(a) Ml (m + M)g

(c) (m+ M)I mgM

(b) mgl(m + M)

(d) (n + M)I Mg

**Answer**

B

**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 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 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 above

**Answer**

C