Class 9th – Gravitation – MASS & WEIGHT

According to Galileo,

       Two bodies of different masses dropped from the same height will touch the floor at the same in the absence of air resistance.

For example, if we drop two objects of masses 5kg and 8kg from same height then both the object will reach at the surface of earth at same time.

This is because g does not depend on the mass of body.

MASS

• Denoted by ‘m’
• Mass of an object is measure of its Inertia.
• Mass is constant
• Its SI unit is Kg.
• It is Scalar quantity.

WEIGHT

• Denoted by ‘W’
• The force of attraction of earth on an object is called weight.
• Weight is not constant
• Its SI Unit is N (Newton)
• It is Vector quantity.

  We know that;    

                                F = m x a

                               & a = g

    Therefore,       F = m x g

                              W = m x g