Question

A ball is thrown vertically upwards with a velocity of 50 m/s. calculate

(a) the maximum height to which it rises.
(b) the total time it takes to return to the surface of earth. (take g =10 m/s2 )

Answer 1

Given, For a vertically thrown upward,

Initial velocity (u) = 50m/s

Final velocity (v) = 0m/s { ∵ the body is thrown vertically upward }

Acceleration due to gravity(a) = -(g)= -10m/s²

Height reached (h) = ? , Time taken (t) = ?

We know that,v² = u²+2as

or, 0² = (50)²+2×(-10)×h { ∵ s=h }

or, 0 = 2500+(-20h)

or, 0 = 2500-20h

or, 20h = 2500

or, h =
`(2500)/(20\\)`

∴ h = 125metres

Also, v = u + at

or, 0 = 50+(-10)×t

or, 0 = 50-10t

or, 10t = 50

or, t =
`(50)/(10)`

∴ t = 5seconds ANS

Hence, The height reached by the ball is 125m and time taken is 5secs.