Question

A ball is dropped from a height of 20m with what velocity and after what time it is strike the ground

Answer 1

Velocity of the ball, g=10m/s

V² = u²+2as

V² = 0+2×10×20

V² = 400

V = 20 m/s

Now time,

V = u+at

t = (v-u)/a

t = (20-0)/10

t = 2 seconds...

Answer 2

A ball is free falling from the height of 20 m

∴ u = o

  a=g

  t = ?

  s = 20 m

∴ s = ut + 1/2at²

 ⇒ 20 = 0×t + 1/2 × 9.8×t²

t² = 40/9.8

t = √(4.081)

t = 2.021 secs

Hence ball took 2 secs to travel from a height of 20 m to the ground.

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