The work done on a body does not depend upon the

A body is dropped from a certain height above the ground.When it is half way down, it possesses

The kinetic energy of a body decreses by 10%.What is the percentage decrease in momentum? 

If the speed of a motor car increases by six times, its kinetic energy will increase by

When you compress a coil spring you do work on it. The elastic potential energy

1 kWh equals

Write an expression for the work done when a force is acting on an object in the direction of its displacement.

Does the transfer of energy take place when you push a huge rock with all your might and fail to move it?Where is the energy you spend going?

What amount of energy in kWh is consumed in 10 h by a machine of power 500W?

A box of about 10 kg is placed at a point A on a horizontal surface.It is moved to a point B which is at a distance of 2m from A.If the line joining A and B is horizontal find the work done by the gravitational force on the box.Justify your answer.

Determine the work done in pushing a cart through a distance of 50 m against the force of friction equal to 150 N.

Explain that the flying bird has potential and kinetic energy and give their expressions.

Work done by a force can be either positive or negative. Lift an object up. Work is done by the force exerted by you on the object. The force of gravity acting on the object in the downward direction.
Answer the following questions based on the above information:
(a) When is the work done by a force positive?
(b) Which one of these forces is doing positive work?
(c) When is the work done by a force negative?
(d) Which force is doing negative work?

The SI unit of energy joule is a small unit. We use a bigger unit of energy called kilowatt hour (kWh). A machine that uses 1000 J of energy every second will consume 1 kWh of energy if it is used continuously for one hour. One kWh is the commercial unit of electrical energy.
Answer the following questions based on the above information:
(a) Name the commercial unit of energy.
(b) Define one kilowatt hour.
(c) Express kilowatt hour in joules.
(d) What will be the energy consumed in 10 hours by a device of 500 W?

Discuss whether or not work is done in the following cases:
(i) When we twist a wire.
(ii) When we press a football.
(iii) When we push a table.
(iv) When a person carries a handbag and walks on a level road.
(v) When a person holds a book in his hand and keeps it stationary.

Define the term energy.Give some examples of bodies possessing some energy.

Name and define the SI unit of power.Give some bigger units of power.

Look at the activities listed below. Reason out whether or not work is done in the light of your understanding of the term 'work':
(i) Suma is swimming in a pond.
(ii) A donkey is carrying a load on its back.
(iii) A wind-mill is lifting water from a well.
(iv) A green plant is carrying out photosynthesis.
(v) An engine is pulling a train.
(vi) Food grains are getting dried in the sun.
(vii) A sailboat is moving due to wind energy.

An object of mass 40 kg is raised to a height of 5m above the ground.What is its potential energy?If the object is allowed to fall, find its kinetic energy when it is half-way down.

Define the term work.State the conditions that need to be satisfied for work to be done.Give some situations in which work is done.

When is the work done by a force said to be (a) positive and (b) negative?Give examples.

(i) A battery lights a bulb.Describe the energy changes involved in the process.
(ii) Calculate the amount of work needed to stop a car of 500 kg moving at a speed of 36 kmh^-1.