Question

A ball is gently dropped from a height of 20 m. If its velocity increases uniformly at the rate of 10 m s-2, with what velocity will it strike the ground? After what time will it strike the ground?

Answer 1

given :-

u (initial velocity) = 0m/s

v (final velocity) = ?

acceleration = 10m/s²

distance = 20m

by using 3rd equation of motion, we get

==> 2as = v² - u²

==> 2 (10) (20) = v² - 0²

==> 400 = v²

==> v = √400

==> v = 20m/s

hence, the ball will strike the ground with a velocity 20m/s

now, we have to find the time taken by the ball.

by using 1st equation of motion, we get

==> v = u + at

==> 20 = 0 + 10t

==> 20/10 = t

==> 2 = t or t = 2

hence, the ball strikes the ground after 2 seconds.

HOPE THIS HELPS..!!