A car falls off a ledge and drops to the ground in `0.5 s`. let` g=10 m//s^(2)` (for simplifyng the calculation).
(i) what is its speed on striking the ground ?

what is its average speed during 0.5s?
(iii) How high is the ledge from the ground ?

Explanation

Time ,`t=(1)/(2)` second
Initial velocity ,`u=0ms^(-1)`
Accelertion due to gravity ,`g=10ms^(-2)`
Acceleration of the car ,`a=+10ms^(-2)`
(downward)
(i) speed v=at
`v=10ms^(-2)xx0.5s`
`=5ms^(-1)`
(ii) average speed `=(u+v)/(2)`
` =(10ms^(-1)+5m s^(-1))//2`
`=2.5 m s^(-1)`
(iii) Distance travelled ,`s=(1)/(2) a t^(2)`
`=(1)/(2)xx10ms^(-2)xx(0.5s)^(2)`
`=(1)/(2) xx10 m s^(-2)xx0.25 s^(2)`
=1.25m
Thus
(i) its speed on strlking th gound
`=5m s^(-1)`
(ii) its average speed during th 0.5 s
`=2.5 ms^(-1)`
(iii) height of the ledge from the ground
`=1.25m.`