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Define work.

Define energy.

Define power.

What is kinetic energy?

What is potential energy?

Give reason for the following :

The potential energy of a freely falling object decreases progressively. Does this violate the law of conservation of energy ? Why?

Pardeep says that the acceleration in an object could be zero even when several forces are acting on it. Do you agree with him? Why?

Why a coolie does not work, when he moves on a level road while carrying a box on his head?

Can a body have momentum without having energy? Explain.

Can there be displacement of an object in the absence of any force acting on it?

Work and energy.

Potential energy and kinetic energy.

Power and horsepower.

Energy and power.

Work and power.

Illustrate the law of conservation of energy by discussing the free fall of a body.

Justify by giving proper reasoning whether the work done in the following cases is positive or negative:

(i) Work done by friction on a body sliding down an inclined plane.

(ii) Work done by a man in lifting a bucket from a well.

A man weighing 70 Kg carries a weight of 10 Kg to the top of tower 100 m high. Calculate the work done.

A block of mass 5 Kg is lying on a frictionless table. A force of 20 N is applied on it for 10 seconds. Calculate its kinetic energy.

A man of mass 60 Kg runs up a flight of 30 steps in 40 seconds. If each step is 20 cm high, calculate the power of the man.

A girl of mass 40 Kg climbs a rope 6 m long at constant speed in 15 seconds. What power does she expend during the climb?

Calculate the kinetic energy of a body of mass 50 Kg moving with a velocity of 50 cm

Does a stationary body possess kinetic energy?

When do you apply more power-when you lift a pen or when you lift a book?

Is any work done by a body moving along a circular path?

A rowing boat upstream is at rest with respect to the shore. Is he doing work?

You pay a coolie for carrying your luggage. Does he really do any work?

When a coil spring is compressed, the work is done on the spring. The elastic potential energy :

Potential energy of a person is minimum when :

No work is done when:

When the speed of a moving object is doubled, its :

When a stone of mass ‘m’ falls through a vertical height ‘d’, the decrease in the gravitational energy is :

A 1 kg mass has a kinetic energy of 1 joule when its speed is:

An iron sphere of mass 30 kg has the same diameter as an aluminum sphere whose mass is 10.5 kg. The spheres are dropped simultaneously from a cliff. When they are 10 m from the ground, they have the same:

An object of mass 1 kg has a potential energy of 1 joule relative to the ground when it is at a height of :

An object of mass 5 kg falls from a height of 5 m above the ground. The loss of potential energy of the mass is :

A weightlifter lifts 240 kg from the ground to a height of 2.5 in 3 second. The average power is :

When a force retards the motion of a body, the work done is :

The work done by a force on a body will be positive if the:

The cgs unit of work is:

One joule work is said to be done when :

The speed of a particle is doubled, its kinetic energy:

Write true or false for the following statements :

When energy changes from one form to another, the energy that disappears from one form, reappears in exactly equivalents amount in the other form.

A force does not work, if it produces no motion.

Kilowatt hour is the unit of power.

Work and energy have different units.

In order to get minimum work, the angle between force and displacement should be 90.

When a body falls on the ground and stops, the principle of conservation of energy is violated.

When velocity is halved, its kinetic energy becomes 1/4^{th}.

When an arrow is released from a bow, potential energy changes into kinetic energy.

Work done by a force depends upon how fast work is done.

The rate of doing work is called power.

Work done by centripetal force is zero.

The unit of work is watt.

If we know the speed and mass of an object we can find out its kinetic energy.