Question

positive nagitive zero work done in one example

Answer 1

Introduction

In our everyday life we use terms like work and energy.

Term work is generally used in context to any kind of activity requiring physical or mental effort.

When we push or pull a heavy load or lift it above the floor then we are doing work, but a man carrying heavy load and standing still is not doing any work according to scientific definition of work.

Another term we often use is energy. Energy is usually associated with work done in the sense that a person feeling very energetic is capable of doing lot of work.

This way energy is defined to be as capacity of doing work.

There are many forms of energy like chemical energy, mechanical energy, electrical energy, heat energy etc. These forms of energies can be used in number of ways.

One form of energy can be converted into another form of energy.

In this chapter we will study about work, relation between work and energy, conservation of energy etc. 

Work

We already know that work is said to be done when a force produces motion.

So we can formally define work done as

Work done by force acting on an object is equal to the product of force and the displacement of the object in the direction of the force.

Work done is defined in such a way that it involves both force applied on the body and the displacement of the body.

Consider the figure given below where a block is placed on a frictionless horizontal floor. This block is acted upon by a constant force F. Action of this force is to move the body through a distance d in a straight line in the direction of force.


Now, work done by this force is equal to the product of the magnitude of applied force and the distance through which the body moves. Mathematically,
W=Fd      

Here both force and displacement have magnitude as well as directions. So both of these quantities are vectors. Work, which is the product of force and displacement, has only magnitude and no direction. So it is a scalar quantity.

If F = 1 N and d = 1 m then the work done by the force will be 1 N m.

Here the unit of work is Newton meter (N m) or joule (J). Thus 1 J is the amount of work done on an object when a force of 1 N displaces it by 1 m along the line of action of the force.

The work done by a force can be either positive or negative or zero.

Answer 2

$hey \: mate \\ \\ here \: i \: s \: ur \: ans$
$positive \: workdone$
Kicking a football.

pushing a box.



$negative \: workdone$
applying force on wall

when u jump work done by gravoty is negative.

when u push spring it relaxes.


$zero \: work \: done$
If u push wall no work done is there

sitting on a chair for hours.



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