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A ball is thrown vertically upwards …

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A ball is thrown vertically upwards with a velocity of 20m/s from the top of a building
  • 1 answers

Yogita Ingle 4 years, 2 months ago

H = u²/(2g)
H = 20²/(2×10)
H = 20 m

The ball will reach 20 m high from the point of projection.
It reaches 20 + 20.5 = 40.5m high from the ground.

(b)
t1 = 2u/g
t1 = 2×20/10
t1 = 4 seconds

If v is the velocity with which it hits the ground then,
v = √(u² + 2aS)
v = √(20² + 2×10×25)
v = 30 m/s

v = u + at
t2 = (v - u)/g
t2 = (30 - 20)/10
t2 = 1 second

Time taken for it to hit the ground = t1 + t2
= 4 + 1
= 5 seconds

Note: I took g = 10m/s².

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