Question

A ball is dropped from a height 20 m per second II ball is thrown down words from the same height after one second with initial velocity you if both the balls reach the ground at same time calculate the initial velocity of the seconnd ball take g=10 metre per second

Answer 1

• A ball is dropped from height of 20m. second ball is thrown downwards from the same height after one second with initial velocity u. if both the balls reach ground at the same time,calculate the initial velocity of the ball. (take g=10m/s
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• For first ball,
• Given height h =20m
• Initial velocity u =0
• Acceleration due to gravity = 10 m/s
• Time taken by ball to fall height h = t
• Using,
• h = ut +0.5 gt
• Here plug in h, u, g to find t =.........?
• 20 = 0.5 *10 *t
• => 20 = 5t
• => t^2 =4
• => t = 2 s
• for 2nd ball
• u' =.....?
• g=10 m/s
• Time taken by 2nd ball to fall a height h t' = (t-1) = 2-1 = 1s
• h = 20m
• Again,
• h = u't' +0.5g(t')^2
• here plug in t',h, g to find u' =........?
• 20 = u'(1) +0.5 (10) *(1)^2
• => 20 = u' + 5
• u' = 20-5 = 15 m/s

Answer 2

Answer:

1. The initial velocity of the second ball = 20m/s

b.) The balls hit the surface with same velocity = 2s

EXPLANATION ::

By the Given condition

Initial velocity of ball = u=0

Final velocity of ball= v (say)

Distance =20m

Acceleration a=10m/s^2

Let Time of fall = t

We know that

v ^2−u^2=2as

v^2−0=2×10×20=400

v=20m/s

Now v=u+at gives

20=0+10×t

t=2s