Question

What is the average speed, over the first 4.0 s of its motion, of a pebble released from rest off a bridge?

Answer 1

Average speed, over the first 4.0 s of its motion, of a pebble released from rest off a bridge = 19.6 m/s

Explanation:

We have equation of motion ,
`s= ut+(1)/(2) at^2`, s is the displacement, u is the initial velocity, a is the acceleration and t is the time.

In this case the initial velocity of body = 0 m/s, acceleration = 9.8
`m/s^2`, we need to calculate displacement when t = 4 seconds.

Substituting

`S=0*t+(1)/(2) *9.8*4^2\\ \\ S=78.4 meter`

So a distance of 78.4 meter has been traveled by pebble in 4 seconds.

Average speed = 78.4/4 = 19.6 m/s