Question

answer this please and why we use third equation of motion.​

Answer 1

Answer:

As

$v {}^{2} - u {}^{2} = 2ah$

So v=0 and a= - g

Putting in the equation we get

$h = \frac{u {}^{2} }{2g}$

Hope it helps

Answer 2

Answer:

We use the third equation of motion because it is the only equation from which we can derive the value u^2/2g