Answer:35.2 ft
Explanation:
Given
height of stick =4 ft
shadow length =2.8 ft
Angle of elevation of sun is

let the height of tree be h
as
will remain same thus


h=35.2 ft

Explanation:
At the top of the tree, the velocity of the pebble is purely horizontal so we can calculate it as


Power = Work / time
The work given here is 83J and the time it took to do 83J of work was 3s
So..
Power = 83J / 3s
Power = 27.67 W or 27.7 W