A particle is projected upwards from the roof of a tower 60 m high with velocity `20 m//s.` Find
(a) the average speed and
(b) average velocity of the particle upto an instant when it strikes the ground. Take `g= 10 m//s^2`

Answer

A, B, D

Explanation

`h=u^2/(2g)=(20)^2/(2xx10)=20m`

Let t be the time when particle collides with ground.
Then using the equation `s=ut+1/2at^2`
we have, `-60=(20)t+1/2(-10)t^2`
Solving this equation, we get
(a) Average speed =`("Total distance")/("Total time")`
`=(20+20+60)/6`
`=16.67 m//s`
Average velocity=`s/t=60/6`
`=10m//s` (downwards)