How long does a ball take to fall from a roof to the ground 7 m below?

1 Answer
Oliver S.
May 7, 2018

See below

Explanation:

If we assume that there is no air resistance and the only force acting on the ball is that of gravity, we can use the equation of motion:

s=ut+(1/2)at^(2)

s=distance travelled
u=initial velocity (0)
t=time to travel given distance
a=acceleration, in this case a=g,the acceleration of free fall which is 9.81 ms^-2

Hence:
7=0t + (1/2)9.81t^2

7=0+4.905t^2

7/(4.905)=t^2

t approx 1.195 s

So it takes barely a second for the ball to hit the ground from that height.

Related questions
See all questions in Falling Objects
Impact of this question
23100 views around the world
You can reuse this answer
Creative Commons License