A ball thrown up from the ground reaches a maximum height of 20m Find : Its initial velocity, the time taken to reach the highest point,its velocity just before hitting the ground ,its displacement between 0.5s"and"2.5s, time when displacement is 15m

A ball thrown up from the ground reaches a maximum height of 20m Find

1.	A ball thrown up from the ground reaches a maximum height of 20m Find : Its initial velocity, the time taken to reach the highest point,its velocity just before hitting the ground ,its displacement between 0.5s"and"2.5s, time when displacement is 15m
Answer» Solution :Using `v^(2)=U^(2)+2as ` for upward MOTION , we get `0^(2)=u^(2)+2(-G)(+20) rArr u=19.8m//s`. `t=((v-u))/a=(0-19.8)/(-9.8)=2.02s` For the complete up - down trip. `v^(2)=u^(2)+2a(0)rArr v^(2)u^(2)rArrv=-u=-19.8m//s` Height at `t=0.5s "is" y_(1)=19.8(0.5)-4.9(0.5)^(2)=8.68m`. Height at `t=2.5s "is " y_(2)=19.8(2.5)-4.9(2.5)^(2)=18.9m` `:.` Displacement `=y_(2)-y_(1)` `=18.9m-8.68m=+10.2m`. `15=19.8t-4.91t^(2)rArrt=1.01s, 3.03s.` at `t=1.01s.` BALL is GOING up and at `t=3.03s,` it is coming down .