Question

A ball is thrown vertically upwards with a velocity of 20m/s from a top of a multistorey building of 25m high.how high will ball rise

Answer 1

This is one dimension motion so ,

initial velocity (u) =20m/s

At highest point it's velocity becomes zero,.

so , final velocity(v) = 0

acceleration is in downward direction I.e acceleration due to gravity

=) a = -g = -10m/s^2

let maximum height reached is "h"

now applying ,

v^2 = u^2 + 2aS

=) 0 = (20)^2 +2(-g)h

= ) h = 400/20

=) h = 20 m

so 20 m high it will rise from multistory building of height 25 m

so height from ground = 20 +25

= 45 m

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Answer 2

Here,

Initial velocity u = 20 m/s

Final velocity v = 0

g = 10 m/s²

We know that,

v² = u² - 2gh

u² - 2gh = 0

h = u² / 2g

h = (20)² / 2 * 10

h = 400 / 20

h = 20 m

Height from the ground = 20 + 25

= 45 m Ans.