Question

The final velocity of a rock dropped from the Empire State Building was 100 m/s. How much time did it take to reach the ground? (neglect air resistance)

Answer 1

t= 10 seconds

Step-by-step explanation:

Using the equation of motion with constant acceleration v=u+at

where t is time

a is acceleration of gravity

u is initial speed and f is final speed.

take the downward direction as negative

`u = 0 \\ v = - 100 (m)/(s) \\ a = - 10 \frac{m}{{s}^(2) }`

then

`- 100 = 0 - 10t \\ - 100 = - 10t \\ t = 10s`