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

Answer:

 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 , $s= ut+\frac{1}{2} at^2$, 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

$S=0*t+\frac{1}{2} *9.8*4^2\\ \\ S=78.4 meter$

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

Average speed = 78.4/4 = 19.6 m/s