Work Power Energy

(Q.1) A particle of mass m is moving on a circular track of

radius r. What is the amount of work done by the particle in moving from A to B ?

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(A) 4mV2 (B) 2mV2 (C) (D) 2m2V2 View Answer (Q.2) In the non-relativistic regime, if the momentum

increases by 100% , the percentage increase in kinetic energy is

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(A) 100 (B) 200 (C) 300 (D) 400 View Answer (Q.3) A 3 kg ball strikes a heavy rigid wall with a speed of 10

m/s at an angle of 60º. It gets reflected with the same speed and angle as shown here. If the ball is in contact with the wall for 0.20s, what is the average force exerted on the ball by the wall?

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(A) 150 N (B) Zero (C) (D) 300 N View Answer (Q.4) A bullet of mass ‘a’ and velocity ‘b’ is fired into a large block of wood of mass ‘c’. The bullet gets embedded into the block of wood. The

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final velocity of the system is

(A) (B) (C) (D) View Answer (Q.5) Two bodies of masses m1 and m2 have equal kinetic energies. If P1 and P2 are their respective momentum, the ratio P1/P2 is equal to

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(A) m1: m2 (B) m2 : m1 (C) (D) View Answer (Q.6) Does potential energy of a spring decreases or increases when it is compressed or stretched?

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View Answer (Q.7) A body of mass m moving with velocity v makes a head

on elastic collision with another body of mass 2m which is initially at rest. The loss of kinetic energy of the colliding body (of mass m ) is

(A)

of its initial kinetic energy

(B)

of its initial kinetic energy

(C)

of its initial kinetic energy

(D)

of its initial kinetic energy

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View Answer (Q.8) A machine gun fires a bullet of mass 40 g with a velocity 1200 ms–1. The man holding it can exert a maximum force of 144 N on the gun. How many bullets can he fire per second at the most?

(A) 2 (B) 4 (C) 1 (D) 3 View Answer

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(Q.9) A ball of mass 5 kg experiences a force F = 2x2 + x. Work done in displacing the ball by 2 m is

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(A) 22/3 J (B) 44/3 J (C) 32/3 J (D) 16/3 J View Answer (Q.10) Consider the following two statements:

I. Linear momentum of a system of particles is zero. II. Kinetic energy of a system of particles is zero.

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Then (A) I imply II but II does not imply I. (B) I does not imply II but II implies I. (C) I imply II and II imply I. (D) I does not imply II and II does not imply I. View Answer ( 1 mark ) (A) Momentum is conserved in elastic collisions but not in inelastic collisions (B) Total kinetic energy is conserved in elastic collisions but momentum is not conserved in elastic (Q.11) Which one of the following statements is true?

collisions

(C) Total kinetic energy is not conserved but momentum is conserved in inelastic collisions (D) Kinetic energy and momentum both are conserved in all types of collisions View Answer (Q.12) Which one of the following statements does hold good when two balls of masses m1and m2undergo elastic collision?

( 1 mark ) (A) When m1 < m2 and m2 at rest, there will be maximum transfer of momentum (B) When m1 > m2 and m2 at rest, after collision the ball of mass m2 moves with four times the velocity of m1 (C) When m1 = m2 and m2 at rest, there will be maximum transfer of K.E. (D) When collision is oblique and m2 at rest with m1 = m2, after collisions the ball moves in opposite direction View Answer (Q.13) If

(A) -5 (B) -3 (C) 4 (D) None of these View Answer

The value of

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(Q.14) A railway carriage of mass 1000 kg moving with a speed of 15 m/s strikes a stationary carriage of the same mass. After the collision, the carriages get coupled and move together. What is their common speed after collision?

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(A) 7.5 m/s (B) 75 m/s (C) 0.75 m/s (D) 750 m/s View Answer (Q.15) Which one is not the unit of energy

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(A) Joule (B) Electron volt (C) Calorie (D) Kilowatt View Answer (Q.16) A truck draws a tractor of mass 1000 kg at a study rate of 20 m/s on a level road .The tension in the coupling is 2000 N. What is the power spent on the tractor?

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(A) 50 kW (B) 45 kW (C) 40 kW (D) 35 kW View Answer (Q.17) A light and a heavy body have equal momentum. Which one has greater K.E.?

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(A) The light body (B) Both have equal K.E (C) The heavy body (D) Data given is incomplete View Answer (Q.18) Two bodies with kinetic energies in ratio 4:1 are moving with equal linear momentum. The ratio of there masses is

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(A) 1:2 (B) 1:1 (C) 4:1 (D) 1:4 View Answer (Q.19) A block of mass 2 kg slides down a curved track that is

one quarter of a circle of radius 1 m. Its speed at the bottom is 4 m/s. Work done by frictional force is (take g = 10 m/s2)

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(A) –4 J (B) 8 J (C) –8 J (D) 20 J View Answer (Q.20) What is the work done by conservative forces over a closed loop?

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View Answer (Q.21) An object moving horizontally with kinetic energy 800 J experiences a constant opposing force of 100 N while moving from a to b (where ab = 2 m)The energy of particle at b is

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(A) 700 J (B) 400 J (C) 600 J (D) 300 J View Answer (Q.22) Name the largest practical unit of energy?

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(A) Joule (B) Electron volt (C) Kilowatt hour (D) None of these View Answer (Q.23) In figure, a carriage P is pulled up from A to B. The

relevant coefficient of friction is 0.40. The work done will be

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(A) 10 kJ (B) 23 kJ (C) 25 kJ (D) 28 kJ View Answer (Q.24) A spring is cut into two equal halves. How is the spring constant

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of each half affected?

View Answer (Q.25) Does work energy theorem applicable everywhere?

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View Answer (Q.26) Define coefficient of restitution?

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View Answer (Q.27) What happens to the potential energy of a body when conservative force does positive work?

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View Answer (Q.28) Can potential energy of an object be negative?

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View Answer (Q.29) What is the work done by earth’s gravitational force in keeping the moon in its orbit?

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View Answer (Q.30) A plot of velocity versus time is shown in the figure. A

single force acts on body. The correct statement is

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(A) In moving from C to D, work done by the force on the body is positive (B) In moving form B to C, work done by the force on the body is positive (C) In moving from A to B, the body does work on the system (D) In moving from O to A, work is done by the body and is negative View Answer (Q.31) The work done by kinetic friction is

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(A) Positive (B) Negative (C) Zero (D) All of these View Answer (Q.32) A motor drives a body along a straight line with a constant force. The power P developed by the motor must vary with time t as

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(A)

(B)

(C)

(D) View Answer (Q.33) Two springs have their force constants k1 and k2. These are extended through the same distance x. If their elastic energies are E1 and E2, then E1 : E2, will be

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(A) (B) (C) k1 : k2 (D) View Answer (Q.34) A particle is moving in a region where potential U is given by U = K(x2 + y2 + z2).The force acting on the particle is

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(A) (B) (C) (D) Zero View Answer (Q.35) A ball is dropped from a height of 1m. If coefficient of restitution between the surface and the ball is 0.6, the ball rebounds to a height of

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(A) 0.6 m (B) 0.4 m (C) 1 m (D) 0.36 m View Answer (Q.36) A small body is projected in a direction inclined at 45º to the horizontal with kinetic energy K. At the top of its flight, its kinetic energy will be

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(A) Zero (B) K/2 (C) K/4 (D) View Answer (Q.37) Calculate the K.E and P.E. of the ball half way up, when a ball of mass 0.1 kg is thrown vertically upwards with an initial speed of 20 ms– 1

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(A) 10 J, 20 J (B) 10 J, 10 J (C) 15 J, 8 J (D) 8 J, 16 J View Answer (Q.38) Two particles A and B of equal masses are suspended from two mass less springs of spring constants k1and k2respectively. If the maximum velocities during oscillation are equal, the ratio of amplitudes of A and B is

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(A) (B) (C) (D) View Answer (Q.39) A force F acting on an object varies with distance x as

shown here. The force is in N and x in m. The work done by the force in moving the object from x = 0 to x = 6 m is

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(A) 18.0 J (B) 13.5 J (C) 9.0 J (D) 4.5 J View Answer (Q.40) A mass of 0.5 kg moving with a speed of 1.5 m/s on a

horizontal smooth surface, collides with a nearly weightless spring of force constant k = 50 N/m. The maximum compression of the spring would be

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(A) 0.5 m (B) 0.15 m (C) 0.12 m (D) 1.5 m View Answer (Q.41) A body of mass 5 kg initially at rest is subject to a force of 10 N. What is the kinetic energy acquired by the body at the end of 20 s?

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(A) 1000 J (B) 2000 J (C) 100 J (D) 4000 J View Answer (Q.42) The human heart discharges 75 ml of blood at each beat against a pressure of 0.1 m of Hg. What is the power of heart assuming that the pulse frequency is 80 beats per minute? .Given density of mercury 13.6x103 kg/m3

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(A) 1.22 watt (B) 1.33 watt (C) 1.44 watt (D) 1.55 watt View Answer (Q.43) Name the smallest practical unit of energy?

(A) Joule (B) Electron volt (C) Kilowatt hour

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(D) None of these View Answer (Q.44) What is the velocity of the bob of a simple pendulum at its mean position, if it is able to rise to vertical height of 10 cm. given g=10 m/s2

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(A) 1.4 m/s (B) 14 m/s (C) 12 m/s (D) 1.2 m/s View Answer (Q.45) The body will attain 1250 Joule K.E. when it falls freely from a height of

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(A) 125 m (B) 250 m (C) 1250 m (D) 2500 m View Answer (Q.46) If momentum of a body increases by 50%, its kinetic energy will increase by

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(A) 50 % (B) 100 % (C) 125 % (D) 150 % View Answer

(Q.47) A constant force

Newton produces a displacement of

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meter. What is work done?

(A) 26 j (B) 23 J (C) 29 J (D) 25 J View Answer (Q.48) A rod elongates by l when a body of mass M is suspended from it. The work done is

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(A) Mgl (B) Mgl (C) 2 Mgl (D) Zero View Answer (Q.49) A box is pushed through 4.0 m across a floor offering 100 N resistances. How much work done by the applied force

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(A) 200 J (B) 300 J (C) 500 J (D) 400 J View Answer (Q.50) An elevator weighing 100 kg is to be lifted up at a constant velocity of 0.5 m/s. What should be the minimum horse power of the motor to be used?

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(A) 0.66 h. p (B) 2 h. p (C) 0.50 h. p (D) 1 h. p View Answer (Q.51) The length of a steel wire increases by 1 cm, when it is loaded with a weight of 10 kg .what is the force constant of the wire if g=10 m/s2 ?

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(A) 105 N/m (B) 102 N/m (C) 104 N/m (D) 103 N/m View Answer (Q.52) A body of mass 2 kg makes an elastic collision with another body at rest and continues to move in the original direction with a speed equal to one third of its original speed. What is the mass of the second body?

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(A) 1 kg (B) 2 kg (C) 3 kg (D) 4 kg View Answer (Q.53) A man pushes a roller with a force of 20 N through a distance of 10 m. What is the work if angle 600 with the ground?

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(A) 50 J (B) 75 j (C) 100 J (D) 200 j View Answer (Q.54) How much mass converted into energy per day in a nuclear power plant operated at 106 kW?

(A) 0.96 g (B) 0.63 g (C) 0.45 g (D) 0.60 g View Answer

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(Q.55) What is work done in holding a 15 kg suitcase while waiting for a bus for?

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(A) 10 J (B) 4 J (C) Zero (D) 15 J View Answer (Q.56) What type of energy is stored in the spring of a watch?

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(A) Kinetic energy (B) Potential energy (C) a & b (D) None of these View Answer (Q.57) A body is moving unidirectionally under the influence of a source of constant power. Its displacement in time t is proportional to

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1/2

(A) t (B) t (C) t3/2 (D) t2 View Answer (Q.58) Which of the following is not conserved in inelastic collision?

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(A) Momentum (B) Kinetic Energy (C) a & b (D) None of these View Answer (Q.59) Springs A and B are identical except that A is stiffer

than B. If both springs are stretched with same force, in which work done will be more.

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View Answer (Q.60) A ball is dropped from height h, and it rebounces to a

height h2. find the Values of Coefficient of restitution.

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View Answer (Q.61) A light body and a heavy body have same momentum,

which will have greater kinetic energy?

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View Answer (Q.62) Define conservative and non conservative forces?

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View Answer (Q.63) Define work energy theorem?

View Answer

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(Q.64) A ball of mass m

moving with velocity v collides head

on with stationary ball of mass m .the velocity of the ball becomes v/4 after the collision.assuming the collision to be elastic find the ratio m

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/m

View Answer (Q.65) what is the height reached by a ball of mass m after

nth collision when it hits the ground with velocity v.given coefficient of restitution is e.

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View Answer (Q.66) A particle of mass 0.5kg travels in a straight line with

velocity v= ax where a= 5ms . What is the work done by the net force, during its displacement from x=0 to x= 2m

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View Answer (Q.67) A uniform chain of mass m and length l is held on

frictionless table such that one third of its length is hanging over the edge.How much work has to be done to pull the hanging part back On the table?

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View Answer (Q.68) If the kinetic energy of a body increases by 300 % by

what % will the linear momentum of body increase?

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View Answer (Q.69) A sphere of mass 2 kg is attached to a string 4 m long

and is whirled in a horizontal circle. The string can withstand a maximum tension of 32 N.calculate maximum velocity of revolution that can be given to the stone without breaking the string.

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View Answer (Q.70) A man has a bag of mass 30kg. First he keeps bag on

his head and moves 10 metre. Secondly, he drags the bag 10 metre on frictionless Surface. In which case, he does more work.

View Answer

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(Q.71) Two bodies of masses 5kg and 3kg moving in the same

direction along the same straight line with velocities 5m/s and 3m/s. respectively suffers one dimensional elastic collision. Find velocities of two bodies after collision.

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View Answer (Q.72) A particle of mass m is moving in horizontal circle of

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radius ‘a’ under a centripetal force equal to p/a2 where P is constant what is the total energy of particle?

View Answer (Q.73) The potential energy as a function of the force

between two atoms in a diatomic molecule is given by U

=

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, where a and b are positive constants and x is the distance between the atoms. find the position of the stable equilibrium for the system.

View Answer (Q.74) The upper half of an inclined plane with inclination

is

perfectly smooth, while the lower half is rough.A particle starting from rest at the top again comes to rest at the bottom. Find the coefficient of friction.

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View Answer (Q.75) Derive an expression for the final velocities if two

bodies of masses m and m collision.

undergo headon elastic

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View Answer

(Q.76) A block of mass m is kept at rough inclined plane

making an angle with the horizontal. Find the velocity of the block when it reaches the bottom. given coefficient of friction is

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View Answer (Q.77) A body of mass M is moving along a straight line by a

machine delivering constant power P. Show that x

t

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View Answer (Q.78) A sphere of mass m moving with a velocity U hits another stationary

sphere of same mass. If e is the coefficient of restitution what is ratio of the velocities of two spheres after collision.