Q.1) Mention some tasks which we do by engaging some animals. Q.2) Does a person going upstairs do any work? Q.3) How much work is done on a moving object when zero net force acts on it? Q.4) In which of the following cases, work is done? I) a crane picks up a fish and flies away 2) a boy tries to push a big rock 3) a body in uniform motion

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(a) When do we say that work is done? Write the formula for the work done by a body in moving up against gravity. Give the meaning of each symbol which occurs in it.

(b) How much work is done when a force of 2 N moves a body through a distance of 10 cm in the direction of force?

The sign of work done by a force on a body is important to understand. State carefully if the following quantities are positive or negative:

(a) work done by a man in lifting a bucket out of a well by means of a rope tied to the bucket.

(b) work done by gravitational force in the above case,

(d) work done by an applied force on a body moving on a rough horizontal plane with uniform velocity,

(e) work done by the resistive force of air on a vibrating pendulum in bringing it to rest.

In which of the following cases is work being done :

(a) A boy pushing a heavy rock

(b) A boy climbing up the stairs

(d) A girl moving on the road.

Fill in the following blanks with suitable words :

(a) Work is measured as a product of ....................... and ..................

(b) The work done on a body moving in a circular path is .....................

(c) 1 joule is the work done when a force of one ............. moves an object through a distance of one.................. in the direction of .....................

(d) The ability of a body to do work is called .................... The ability of a body to do work because of its motion is called .................

(e) The sum of the potential and kinetic energies of a body is called ......... energy.

A force of 12 N is acting on a body and the same force 12 N is acting on the same body but in a different direction. If the body moves with a displacement of $^{'} d^{'}$ metres, then what is the work done?

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