Question

Question #189b5

Answer 1

Let downward initial velocity of the pebble be `u`

So utilising `h=uxxt+1/2xxgxxt^2` we get

`91.2=uxx4+1/2xx9.8xx4^2`

`=>4u=91.2-8xx9.8`

`=>u=91.2/4-8xx9.8/4`

`=>u=22.8-19.6=3.2"m/s"`