Question

A stone is thrown horizontally with a speed of 15 m/s from the top of a vertical cliff at the edge of a lake. If the stone hits the water 2.0 s later, the height of the cliff is closest to

Answer 1

20 m

Explanation:

We are given that

Initial horizontal speed ,
`u_x=15 m/s`

Time, t=2 s

Initial vertical velocity,
`u_y=0`

We know that

`h=u_yt+(1)/(2)gt^2`

Where
`g=-9.8m/s^2`

Using the formula

`h=0(2)+(1)/(2)(-9.8)(2)^2`

`h=-19.6 m\approx -20 m`

The negative sign indicates that the displacement of stone is in downward direction.

Hence, the height of the cliff is closest to 20 m