The stone is thrown at an angle to the horizon at a speed of 10 m / s. Determine at what height the speed

The stone is thrown at an angle to the horizon at a speed of 10 m / s. Determine at what height the speed of the stone will be halved.

Given:
V = 10 m / s
Find: h -? – height, where v will be half as much.
Decision:
It is known that the kinetic energy of a stone will decrease by half at a height h, at which
v1 = 1/2 v
In other words, using the law of conservation of energy, you can find:
mv ^ 2/2 = mv1 ^ 2/2 + mgh
Let us express h from here:
h = 1 / 2g (v ^ 2 – v1 ^ 2) = 3v ^ 2 / 8g
Substitute the known values:
h = 3 * 10 ^ 2/8 * 10 = 300/80 = 30/8 = 15/4 = 3.75 m
Answer: 3.75