Velocity versus time graph of a ball of mass 50 g rolling on a concrete floor is shown in Fig. 9.1. Calculate the acceleration and frictional force of the floor on the ball.
Given, m = 50g
F =?
We know, Force = mass × acceleration
= 
* 10 = 0.5 N
The velocity of the ball zero time is 80ms-1. It decelerates due to the friction of the floor with itself and comes to rest after 8 seconds.
a = 
= 
= -10m/s2
The negative sign indicates that the frictional force exerted opposes the motion of the ball. Now, using Newton’s relation,
F = m× a
= 
× -10
= -0.5 N
15