# Important physical Quantities

## Important physical Quantities

It is profitable to give a brief description of the following physical quantities much used in science and Engineering:-

### Force:-  It is thr product of mass (kg) and acceleration (m/s^2). The unit of force is newton (N); being the force required to accelerate a mass of 1 kg through an acceleration of 1m/s^2).

F= m a newtons
Where m = mass of a body in kg
a = acceleration in m/s^2

### Weight:- The force with which a body is attraction towards the centre of earth is called the weight of the body . Now,

Force = mass × acceleration.
• If m is mass of a body in kg and g is the acceleration due to to gravity in m/s^2 , then
Weight , W = m g newtons

• As the value of g varies from place on earth's  surface , therefore , the weight of the body varies accordingly. However, for practical purposes, we take g = 9.81 m/s^2 so that weight of the body = 9.81 m newtons. Thus if a mass of 1 kg rests on a table , the downward force on the table i.e., weight of thr body is W = 9.81 × 1 = 9.81 newtons.