Work, Energy and Power quiz

Work is a:

The work done by friction on a sliding body is usually:

1 kilowatt-hour is equal to:

If the speed of a body is doubled, its kinetic energy becomes:

In an elastic collision:

Linear momentum is conserved in:

An example of a conservative force is:

The work done by a force perpendicular to the displacement is:

The SI unit of power is:

A body of mass 2 kg has momentum 10 kg m/s. Its kinetic energy is:

Define the scalar product of two vectors. (2 marks)

Find the work done by a force of 10 N at 60 degrees to the displacement over a distance of 5 m. (2 marks)

Distinguish between conservative and non-conservative forces. (2 marks)

Why is no work done by gravity on a satellite in a circular orbit? (2 marks)

What is the kinetic energy of a 2 kg body moving at 3 m/s? (2 marks)

Find the potential energy of a 5 kg body at a height of 10 m. (2 marks)

Distinguish between elastic and inelastic collisions. (2 marks)

Show that KE = p^2/(2m). (2 marks)

State the law of conservation of mechanical energy. (2 marks)

A body slides from rest down a frictionless incline from a height of 5 m. Find its speed at the bottom. (2 marks)

A raindrop of mass 1.00 g falls from a height of 1.00 km and hits the ground at 50 m/s. Find the work done by gravity and by air resistance. (3 marks)

An elevator of total mass 1800 kg moves up at a constant speed of 2 m/s against a friction force of 4000 N. Find the minimum power delivered by the motor. (3 marks)

A 2 kg ball moving at 4 m/s hits a 1 kg ball at rest in a one-dimensional elastic collision. Find their velocities after the collision. (3 marks)

A force F = (5 - x) N acts on a body as it moves from x = 0 to x = 4 m. Find the work done. (3 marks)

A man of 60 kg climbs 10 m of stairs in 15 s. Find his power. (3 marks)

Read the passage and answer the questions. A roller coaster car of mass 500 kg starts from rest at a height of 30 m. Ignore friction. (i) Find its potential energy at the top. (ii) Find its speed at the lowest point. (iii) Find its speed at a height of 10 m. (5 marks)

Read the passage and answer the questions. A hydroelectric plant has water falling 50 m at a rate of 2000 kg per second. (i) Find the potential energy lost by the water per second. (ii) If the plant is 80% efficient, find its electrical power output. (iii) Name the energy changes involved. (5 marks)

Read the passage and answer the questions. A car of mass 1200 kg moving at 20 m/s brakes to a stop. (i) Find its initial kinetic energy. (ii) Find the work done by the brakes. (iii) Where does this energy go? (5 marks)

Read the passage and answer the questions. Two identical carrom coins collide head-on. One is moving at 2 m/s and the other is at rest. The collision is elastic. (i) Find the velocity of the first coin after the collision. (ii) Find the velocity of the second coin. (iii) Show that kinetic energy is conserved. (5 marks)

Read the passage and answer the questions. A student pushes a 10 kg box 4 m along a floor with a horizontal force of 50 N. The friction force is 30 N. (i) Find the work done by the student. (ii) Find the work done by friction. (iii) Find the gain in kinetic energy of the box. (5 marks)

Define work done by a constant force and by a variable force. Explain positive, negative and zero work with examples. (6 marks)

Explain potential energy and conservative forces, and show that mechanical energy is conserved for a freely falling body. (6 marks)

Derive the expression for the potential energy of a spring and explain the energy changes in a block-spring system. (6 marks)

Define power. Show that P = F.v and explain the commercial unit of energy. (6 marks)

Explain elastic and inelastic collisions in one dimension, and introduce collisions in two dimensions using conservation of momentum. (6 marks)