Question

A girl is on a bridge 38.4 m high.

She throws a rock straight down at
-12.5 m/s. How long does it take the
rock to hit the ground?
(Unit = s)
Time (s)

Answer 1

Step-by-step explanation:

DOWN at -12. 6 is UP at 12.6 m/s

I will assume you meant the downward velocity is 12.6 m/s

The distance traveled , d (38.4 m ) is given by

d = do + vot + 1/2 at2 do = 0 vo = 12.6 m/s a = 9.81 m/s2

38.4 = 0 + 12.6t + 1/2 * 9.81 t2

4.905 t2 + 12.6t - 38.4 = 0

Using quadratic formula with a = 4.90 b= 12.6 c= -38.4

you will find t= 1.79 s