Question

Solved E xample 1. An iron ball of mass 3 kg is leased from a height of 125 m and falls eely to the ground. Assuming that the alue of g is 10 m/s, calculate time taken by the ball to reaching the ground the height of the ball at half the time it taken to reach the ground ?

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Answer 1

Answer:

$\sf \: S=125=UT+ \frac{1}{2} AT^2$

as U is =0

$\sf \: therefore S= \frac{1}{2} AT^2$

$\sf \: here \: A \: is \: 10m/s^2$

therefore

$\sf \: 125= \frac{1}{2} AT^2$

$\sf \: 250=10T^2$

therefore T =√25=5sec

$\sf \: V^2-U^2=2AS$

here A is -10 and S is -125m as its falling from a height and U =0 therefore

$\sf \: V^2=2(-10)(-125)$

V=√2500

V=50m/s

$\sf \: half \: time \: by \: it \: reaches = \frac{5}{2} =2.5sec$

$\sf \: S=UT + \frac{1}{2} AT^2$

$\sf \: S= \frac{1}{2} x \: 10xT^2$

therefore S=31.25m

but H=125-31.25

therefore H=93.75m

a)The time by which the ball reaches the ground is=5seconds

b) The velocity of the ball on reaching the ground=50m/s

c) The height of the ball at half time it takes to reach the ground=93.75m