Question

A ball is gently dropped from a height of 20m.If its velocity increase uniformly at the rate of 10m/s, with what velocity will it strike the ground? After what time will it strike the ground?​

Answer 1

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Given:-

Initial velocity of ball(u) = 0

Final velocity of ball (v) = ?

Distance through which ball falls (s) = 20m

Acceleration (a) = 10m/s

Time of fall (t) = ?

We know,

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

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

${v}^{2} = ( {0)}^{2} + 2 \times 10 \times 20$

${v}^{2} = 400$

$v = \sqrt{400} = 20$

$v = 20 {ms}^{2}$

we know that,

v = u + at

= 20 = 0 +10 × t

= 10 t = 20

t = 28