JEE Physics Work Energy and Power MCQs Set A

Question:

• a) –8 J
• b) +8 J
• c) –4 J
• d) +4 J

Answer: –8 J

Question:

• a) 25 J
• b) –50 J
• c) – 15 J
• d) 15 J

Answer: 25 J

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: 50 J

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: Lifts it vertically upwards

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: 60°

Question:  A block of mass m is pulled along a circular arc by means of a constant horizontal force F as shown. Work done by this force in pulling the block from A to B is

• a)

  

• b)

  

• c)

  

• d) None of this

Answer:

Question:

• a) 8 J
• b) 12 J
• c) 36 J
• d) 10 J

Answer: 8 J

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: May be positive, negative or zero

Question:

• a)

  

• b) 16 J
• c) 160 J
• d) 1600 J

Answer: 

Question:

• a) 11
• b) 20
• c) 21
• d) Infinite

Answer: 11

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: 135

Question:

• a) 4a²
• b)

  

• c) 2a²
• d) a²

Answer: 4a²

Question:

• a) Zero
• b) 2 J
• c) 4 J
• d) 8 J

Answer: Zero

Question:  A uniform chain of length L and mass M is lying on a smooth table and one third of its length is hanging vertically down over the edge of the table. If g is acceleration due to gravity, the minimum work required to pull the hanging part of the chain on the table is

• a)

  

• b)

  

• c)

  

• d) MgL

Answer:

Question: Two bodies of masses m₁ and m₂ have same kinetic energy. The ratio of their momentum is

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: Two bodies of masses m₁ and m₂ have same momentum. The ratio of their KE is

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

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: 20%

Question: When momentum of a body increases by 200%, its KE increases by

• a) 800%
• b) 400%
• c) 300%
• d) 200%

Answer: 800%

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: KE acquired by a mass m in travelling a certain distance d, starting from rest, under the action of a constant force F is

• a) None of these
• b) Directly proportional to m
• c)

  

• d)

  

Answer: None of these

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

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: Always

Question: Potential energy is defined

• a) Only in conservative fields
• b) As the negative of work done by conservative forces
• c)

  

• d) All of these

Answer: Only in conservative fields

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

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: 15U

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: Initially mass m is held such that spring is in relaxed condition. If mass m is suddenly released, maximum elongation in spring will be

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: A block of mass m moving with velocity v₀ on a smooth horizontal surface hits the spring of constant k as shown. The maximum compression in spring is

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: For a particle moving under the action of a variable force, kinetic energy-position graph is given, then

• a) At D particle has maximum acceleration
• b) At B particle is accelerating
• c) At A particle is decelerating
• d) At C particle has maximum velocity

Answer: At D particle has maximum acceleration

Question:  A particle of mass 0.1 kg is subjected to a force which varies with distance as shown. If it starts its journey from rest at x = 0, then its velocity at x = 12 m is

• a) 40 m/s
• b)

  

• c)

  

• d) 0 m/s

Answer: 40 m/s

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: 1.5x

Question: Initially mass m is held such that spring is in relaxed condition. If mass m is suddenly released, maximum elongation in the spring will be

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

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: 1200 litre

Question:

• a) 30 W
• b) 20 W
• c) 10 W
• d) 5 W

Answer: 30 W

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: Increases

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: A body of mass m accelerates uniformly from rest to velocity v₁in time interval T₁. The instantaneous power delivered to the body as a function of time t is

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

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: 50 kW

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: A car of mass m has an engine which can deliver power P. The minimum time in which car can be accelerated from rest to a speed v is

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

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: 100 kW

Question: On a particle placed at origin a variable force F = –ax (where a is a positive constant) is applied. If U(0) = 0, the graph between potential energy of particle U(x) and x is best represented by

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: The variation of potential energy U of a system is shown in figure. The force acting on the system is best represented by

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: The variation of potential energy U of a body moving along x-axis varies with its position (x) as shown in figure

The body is in equilibrium state at

• a) B
• b) C
• c) A
• d) None of this

Answer: B

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: 4.47 ms^–1, zero

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: 1.56 N

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: 8 m/s

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: 32 J

Question: A ball of mass m moving with velocity v collides head-on with the second ball of mass m at rest. If the coefficient of restitution is e and velocity of first ball after collision is v₁ and velocity of second ball after collision is v₂ then

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

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: 3m_A= m_B

Question:

• a)

  

• b)

  

• c) 2 v
• d) v

Answer:

Question: A particle of mass m moving towards west with speed v collides with another particle of mass m moving towards south. If two particles stich to each other, the speed of the new particle of mass 2 m will be

• a)

  

• b)

  

• c)

  

• d) v

Answer:

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: 30 J

Question: A stationary particle explodes into two particles of masses x and y, which move in opposite directions with velocity v₁ and v₂. The ratio of their kinetic energies (E₁: E₂) is

• a)

  

• b)

  

• c)

  

• d) 1

Answer:

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: The momentum of a ball colliding elastically with the floor is conserved

Question: A bullet of mass m moving with a velocity u strikes a block of mass M at rest and gets embedded in the block. The loss of kinetic energy in the impact is

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: A bullet of mass m moving with velocity v strikes a suspended wooden block of mass M. If the block rises to height h, the initial velocity of the bullet will be

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

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: 6 m

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: 60 cm/s