Q1 of 28 Page 159

Define work and write its units.

In science, we define Work as product of the Force(F) & the Displacement(s) moved along the direction of force

W = Force Displacement -- (i)


This formula for work used in only Translatory motion of the object.


Work has only Magnitude, no Direction. So, work is a Scalar quantity.


The SI unit of Force(F) is Newton(N) and Displacement(s) is meter(m).


Putting 1N and 1m in formula of work eq(i), work done comes out to be 1N-m.Hence unit of work is newton-meter(N-m) or joule(J).



Fig - Work done in moving a block through a distance ‘s’ and by appling force’F’


More from this chapter

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2

Give few examples where displacement of an object is in the direction opposite to the force acting on the object.

 3

Identify the wrong statement among the following. Rewrite them by making necessary corrections.

a) Work and energy have different units.


b) When an aero plane takes off, the work done by its weight is positive.


c) The potential energy of spring increases when it is extended and decreases when it is compressed.


d) If the work done by external forces on a system is negative then the energy of the system decreases.


e) When a body is falling freely from a height, its kinetic energy remains constant.


f) The unit of power is watt.

 4

What is mechanical energy?

 5

State the principle of conservation of energy.