Seema tried to push a heavy rock of 100 kg fro 200 s but could not more it.Find the work done by Seema at the end of 200 s.

2

(a)

A pair of bullocks exerts a force of 140N on a plough.The field being ploughed is 15 m long.How much work is done in ploughing the length of the field?

2

(a)

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

2

(a)

The work done on a body of mass 10 kg to lift it through a certain height is 490J.Calculate the height through which the body is lifted.Take g = 9.8 m/s².

2

(a)

If the work done by a force in moving an object through a distance of 40 cm is 48.4J, what is the magnitude of the force ?

2

(a)

State two factors on which the kinetic energy of a moving body depends.

2

(a)

What change should be affected in the velocity of a body to maintain the same kinetic energy if its mass is increased four times?

2

(a)

Calculate the kinetic energy of a ball of mass 10 g and momentum 100 g cm/s.

2

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Find the momentum of a body of mass 100g having kinetic energy of 20J.

2

(a)

Can you say if the following objects have energy? If they do, identify whether the energy is kinetic, potential or combination of the two:
(i) ceiling fan which has been switched off.
(ii) A man climbing a hill.
(iii) A flying bird.
(iv) Water in the reservoir of a dam.
(v) A spring expanded beyond its normal shape.
(vi) A rubber band lying on a table.
(vii) A stretched rubber band lying on the ground.

2

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What kind of energy transformations takes place when a body is dropped from a certain height?Explain.

2

(a)

Two masses m and 2m are dropped from heights h and 2h.On reaching the ground, which will have a greater kinetic energy and why?

2

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A man does 50 J of work in 5 seconds. What is the power?

2

(a)

The work done by the heart for each beat is 1 joule.Calculate the power of the heart if it beats 72 times in a minute.

2

(a)

The heart does 1.5J of work in each heart beat.How many times per minute does it beat if its power is 2 watt?

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(a)