Q. A stone dropped from a window reaches the ground in 0.5 seconds -

i) calculate its speed just before it reaches the ground?

ii) what is its average speed during 0.5 sec?

iii) calculate the height of window from the ground?

Here,

Initial speed, u = 0

Acceleration, a = 9.8 m/s^{2}

Time, t = 0.5 s

(i)

Using, v = u + at

=> v = 0 + (9.8)(0.5)

=> v = 4.9 m/s

This is the speed when the stone reaches the ground.

(ii)

Distance traveled, s = ut + ½ at^{2}

=> s = 0 + ½ (9.8)(0.5)^{2}

=> s = 1.225 m

So, average speed = 1.225/0.5 = 2.45 m/s

(iii)

Height of window from the ground is 1.225 m

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