Question

A rock is dropped from a 164-m-high cliff. How long does it take to fall (a) the first 82.0 m and (b) the second 82.0 m

Answer 1

Step-by-step explanation:

Given

Rock is dropped from a height of
`h=164\ m`

Rock is drooped so initial velocity is zero i.e.
`u=0`

Time taken to fall
`82\ m` is given by

`y=ut+(1)/(2)at^2`

where

y=displacement

u=initial velocity

a=acceleration

t=time

`164=0+(1)/(2)gt^2`

`t=\sqrt{(2* 82)/(9.8)}`

`t=4.09\ s`

Now time taken to fall another 82 m

We can calculate this time by first calculating time taken to cover 82+82 m and then subtracting the time taken to cover 82 m

`t_2=\sqrt{(2* 164)/(9.8)}`

`t_2=5.78\ s`

time taken
`=t_2-t=5.78-4.09=1.69\ s`