Question

A ball is dropped from the roof of a building takes 0-2sec to pass a window 3m in height.How far is the top of the window below the roof?

Answer 1

This should be the correct answer. Hope it will be helpfull to u.

#the failure

Answer 2

The correct answer is 3.64m.

Given: Time taken to pass the window = 2 sec.

Height of window = 3m.

To Find: Distance between top of window and roof.

Solution:

Initial velocity = u

Final velocity = v

Distance covered = 3m

Time taken = 2sec

Acceleration = 10 m$s^{2}$

From equation of motion,

s = ut + $\frac{1}{2} at^{2}$

3 = u*2 + $\frac{1}{2}*10*2^{2}$

2u = 17

u = 8.5 $ms^{-1}$

Now, imagine the ease from building top to windows top.

Initial velocity = 0

Final velocity = 8.5 $ms^{-1}$

Time taken = 2sec

Acceleration = 10 m$s^{2}$

Again using equation of motion.

$v^{2} =u^{2} +2as$

$8.5^{2} =0^{2} +2*10*H$

72.25 = 20H

H = 3.64 m

Hence, the distance between top of window and roof is 3.64m.

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