Question

A certain force exerted for 1.2 s raises the speed of an object from 1.8 m/s to 4.2 m/s. Later, the same force is applied for 2 s. How much does the speed change in 2 s.

Answer 1

t = 1.2 s; u = 1.8 m/s; v = 4.2 m/s

acceleration a = \(\frac{v-u}{t}\)

= \(\frac{4.2 - 1.8}{1.2}\) = \(\frac{2.4}{1.2}\)

= 2 m/s²

Now, the force applied is the same, it will produce the same acceleration.

Change in speed = acceleration x time for which force is applied.

= 2 x 2 = 4 m/s

change in speed = 4 m/s.