Two balls are dropped to the ground from different heights .One ball is dropped 2.0 s after the other,but both strike the ground at the time 5.0s after the 1st is dropped .(a) What is the different in the heights from which they were dropped? (b)From what height was the first ball dropped ?

Explanation

(a)For the first ball s=`h_(1)`,v=0,t=5 sec
`s=ut+(1)/(2)at^(2),h_(1)=0xx5+(1)/(2)9.8xx5^(2)=122.5m`
For the second ball s=`h_(2)`,u=0,t=3 sec `therefore h_(2)(1)/(2) "gt"^(2)=(1)/(2)xx9.8xx9=4.9xx9=44.1m`
Difference in heights `h=h_(2)-h_(t)=122.5-44.1=78.4m`
(b)The first ball was dropped from a height of `h_(1)`=122.5m.