Question

Please answer it in a sentence from the picture below?

Answer 1

7 seconds in air and 5 seconds in water

Explanation:

First thing to do is to draw a diagram.

Let the distance from the cliff to the sea be `h "m"`, and the time taken to drop this be `t"s"`. This would mean the distance from the sea to the seabed is `(127-h)"m"` and the time taken is `"(12-t)"s"`

We can use `"speed"="distance"/"time"` to make two equations to solve simultaneously.

For air:

`16=h/t`
`h=16t" " (1)`

For water:

`3=(127-h)/(12-t)`
`3(12-t)=127-h`
`36-3t=127-h`
`-3t=91-h`
`3t=h-91" " (2)`

Substituting `(1)` into `(2)` we get:

`3t=16t-91`
`-13t=-91`
`13t=91`
`t=7`

So the stone drops for 7 seconds in air.

Since the total time the stone drops for is `12"s"`, the time taken for it to fall in the water `=12-7=5"s"`