Difference between mass and weight

Weight is the force due to gravity on a mass. So, mass remains constant but weight changes according to  the change in the gravitational field.

                W = mg or m = W/g

Solved Examples 

1. Calculate the mass of a body if the density and volume of a body are 2 Kg/m³ and 5 m³.

Ans:

Here mass = density x volume

                  = 2 x 5

                  = 10 Kg

2. If an object is moving with a velocity of 5 m/s and has a kinetic energy of 100J, Find the mass.

Solution: We know that KE = ½ mv²

100 = ½ x m x 5 x 5

100 = 25 m/2

m = 100×2/25 = 200/25 = 8 kg