Question

A ball is rolled on a flat surface with an initial velocity of 2 m/s. what is the ball's acceleration if it was found 15 meters away from its starting position after 5 seconds? What is the ball's velocity at a distance 20m? how long will the ball travel to achieve a velocity of 20 m/s?

Answer 1

(a)

$$d=v_0t+at^2/2$$

$$a=2(d-v_0t)/t^2=2(15-2*5)/5^2=0.4\:\rm m/s^2$$

(b)

$$v=v_0+at$$

$$t=\frac{v-v_0}{a}=\frac{20-2}{5}=3.6\:\rm s$$