Question

A ball is thrown vertically downward with a
velocity of 20 m/s from the top of a tower. It hits
the ground after some time with a velocity of
80 m/s. The height of the tower is: (g=10 m/s2)
(1)
320 m
300 m
(2)
360 m
(3)
(4)
340 m​

Answer 1

$answer$

Taking downward direction to be positive.

Initial velocity u=−10 m/s

Final velocity v=30 m/s

Let the height of the tower be H.

Acceleration a=g=10 m/s²

using v²-u²=2as

30²-(-10)²

=2×10 ×H

⟹ H=40 m

Answer 2

Answer:

u=20m/s

v=80m/s

a=10m/s²

v²=u²+2as

80²=20²+2(10)s

6400=400+200s

200s=6000

s=6000/200

s=30m

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