JEE Physics Work Energy and Power MCQs Set A

Question. If 250 J of work is done in sliding a 5 kg block up an inclined plane of height 4 m. Work done against friction is (g = 10 ms^–2)
(a) 50 J
(b) 100 J
(c) 200 J
(d) Zero

Answer: A

Question. A man carries a load on his head through a distance of 5 m. The maximum amount of work is done when he
(a) Lifts it vertically upwards
(b) Moves it over an inclined plane
(c) Moves it over a horizontal surface
(d) None of these

Answer: A

Question. A body moves a distance of 10 m along a straight line under the action of a force 5 N. If the work done is 25 joule, the angle which the force makes with the direction of motion of body is
(a) 60°
(b) 90°
(c) 30°
(d) 0°

Answer: D

Question. Work done by frictional force
(a) May be positive, negative or zero
(b) Is always positive
(c) Is always negative
(d) Is zero

Answer: A

Question. A particle moves along x-axis from x = 0 to x = 5 metre under the influence of a force F = 7 – 2x + 3x². The work done in the process is
(a) 135
(b) 70
(c) 270
(d) 35

Answer: D

Question. KE of a body is increased by 44%. What is the percent increase in the momentum?
(a) 20%
(b) 10%
(c) 30%
(d) 44%

Answer: A

Question. When momentum of a body increases by 200%, its KE increases by
(a) 800%
(b) 400%
(c) 300%
(d) 200%

Answer: A

Question. The total work done on a particle is equal to the change in its kinetic energy. This is applicable
(a) Always
(b) Only in inertial frames
(c) Only if the conservative forces are acting on it
(d) Only when pseudo forces are absent

Answer: A

Question. A spring with spring constants k when compressed by 1 cm, the potential energy stored is U. If it is further compressed by 3 cm, then change in its potential energy is
(a) 15U
(b) 8U
(c) 9U
(d) 3U

Answer: A

Question. An unloaded bus can be stopped by applying brakes on straight road after covering a distance x. Suppose, the passenger add 50% of its weight as the load and the braking force remains unchanged, how far will the bus go after the application of the brakes? (Velocity of bus in both case is same)
(a) 1.5x
(b) Zero
(c) 2x
(d) 2.5x

Answer: A

Question. The power of water pump is 4 kW. If g = 10 ms^–2, the amount of water it can raise in 1 minute to a height of 20 m is
(a) 1200 litre
(b) 2000 litre
(c) 1000 litre
(d) 100 litre

Answer: A

Question. A body is projected from ground obliquely. During downward motion, power delivered by gravity to it
(a) Increases
(b) Remains constant
(c) Decreases
(d) First decreases and then becomes constant

Answer: A

Question. The power of a pump, which can pump 500 kg of water to height 100 m in 10 s is
(a) 50 kW
(b) 500 kW
(c) 25 kW
(d) 75 kW

Answer: A

Question. From a water fall, water is pouring down at the rate of 100 kg/s, on the blades of a turbine. If the height of the fall is 100 m, the power delivered to the turbine is approximately equal to
(a) 100 kW
(b) 10 kW
(c) 1 kW
(d) 100 W

Answer: A

Question. A particle of mass 200 g is moving in a circle of radius 2 m. The particle is just ‘looping the loop’. The speed of the particle and the tension in the string at highest point of the circular path are (g = 10 ms^–2)
(a) 4.47 ms^–1, zero
(b) 4 ms^–1, 5 N
(c) 2.47 ms^–1, zero
(d) 1 ms^–1, zero

Answer: A

Question. A particle of mass 200 g, is whirled into a vertical circle of radius 80 cm using a massless string. The speed of the particle when the string makes an angle of 60° with the vertical line is 1.5 ms^–1. The tension in the string at this position is
(a) 1.56 N
(b) 1 N
(c) 2 N
(d) 3 N

Answer: A

Question. A stone of mass 1 kg is tied with a string and it is whirled in a vertical circle of radius 1 m. If tension at the highest point is 14 N, then velocity at lowest point will be
(a) 8 m/s
(b) 6 m/s
(c) 4 m/s
(d) 3 m/s

Answer: A

Question. An object of mass 80 kg moving with velocity 2 ms^–1 hit by collides with another object of mass 20 kg moving with velocity 4 ms^–1. Find the loss of energy assuming a perfectly inelastic collision
(a) 32 J
(b) 30 J
(c) 24 J
(d) 12 J

Answer: A

Question. Particle A makes a perfectly elastic collision with another particle B at rest. They fly apart in opposite direction with equal speeds. If their masses are m_A & m_B respectively, then
(a) 3m_A= m_B
(b) 2m_A= m_B
(c) Both
(d) None of these

Answer: A

Question. A body of mass 10 kg moving with speed of 3 ms^–1 collides with another stationary body of mass 5 kg. As a result, the two bodies stick together. The KE of composite mass will be
(a) 30 J
(b) 60 J
(c) 90 J
(d) 120 J

Answer: A

Question. Select the false statement
(a) The momentum of a ball colliding elastically with the floor is conserved
(b) In an oblique elastic collision between two identical bodies with one of them at rest initially, the final velocities are perpendicular
(c) The coefficient of restitution for a collision between two steel balls lies between 0 and 1
(d) In elastic collision, KE is not conserved during the collision

Answer: A

Question. A ball is allowed to fall from a height of 10 m. If there is 40% loss of energy due to impact, then after one impact ball will go up by
(a) 6 m
(b) 4 m
(c) 8 m
(d) 10 m

Answer: A

Question. A bullet weighing 10 g and moving with a velocity 300 m/s strikes a 5 kg block of ice and drop dead. The ice block is kept on smooth surface. The speed of the block after the collision is
(a) 60 cm/s
(b) 6 cm/s
(c) 6 m/s
(d) 0.6 cm/s

Answer: A