Question

A ball is dropped gently from a ht of 400m if it's velocity increase uniformly at the rate of the 20m/ssq.. If it's velocity will strike the ground? After what time will it strike the ground?

Answer 1

s = 400m
a = 20 m/s^2
u = 0
v = ?

We know that
v^2 - u^2 = 2as

Or v^2 - 0 = 2×20×400

Or v^2 = 16000

Or v = √16000

Or v = 40√10 m/s


Also v = u + at

Or 40√10 = 0 + 20t

Or t = 40√10 / 20

Or t = 2√10 second


Hence it will strike the ground at velocity 40√10 m/s after 2√10 seconds.