Question

Rhoda tiller looks up to see a flowerpot fall off a ledge 9.2 m above her head. How long does she have to react and move before being hit on the head?

Answer 1

The flowerpot is in free fall, so it moves by uniformly accelerated motion with acceleration equal to
`g=9.81 m/s^2`. Its initial speed is zero, so we can write the law of motion for the pot as

`S(t) = (1)/(2)gt^2`
where S(t) is the distance covered by the pot after a time t.
We want to find the time t at which the pot reaches ground, so the time t after which the pot has covered 9.2 m, therefore we should require S(t)=9.2 m and find t:

`9.2 m= (1)/(2) gt^2`

`t= \sqrt{ (2 \cdot 9.2m)/(9.81 m/s^2) }=1.37 s`