Question

Q. A stone is dropped from the window of a bus moving at 60 km/hr. If the window is 196cm high, what is the distance along the track which the stone moves before striking the ground ?

Answer 1

Let's get our units consistent.
Acceleration due to gravity: `g = 9.8 m/s^2`
Speed: `60 cancel(km)/cancel(hr) * (1000 m)/(1 cancel (km)) * (1 cancel(hr))/(3600 s) = 16.67 m/s`
Distance to fall: `196 cancel(cm) * (1 m)/(100 cancel(cm)) = 1.96 m`

We need the time to hit the ground, so we need the formula

`y = u*t + 1/2*a*t^2`

`1.96 m = 0 + 1/2*9.8 m/s^2*t^2`

`t^2 = (2*1.96 cancel(m))/(9.8 cancel(m)/s^2) = 0.4 s^2`

`t = 0.632 s`

Now we can calculate the distance down the road it travels in that time. It is

`d = 16.67 m/cancel(s) * 0.632 cancel(s) = 10.5 m`

I hope this helps,
Steve