In: Physics
5. You throw a ball into the air. It takes 6.0 ? for the ball to reach your hand.
a. Determine the initial speed at which the ball was thrown.
b. Determine the final velocity of the ball when it hits your hand.
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b)
Note that there has been no energy loss to the ball, so according to energy conservation law, the kinetic energy of the ball should remain same when you first throw it up and when it reaches back to your hand. So, initial and final velocity will have same magnitude although the direction would be different.
So, final velocity = -29.4 m/s.
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You can also calculate it using Newton's laws of motion equation -
So, when the ball reaches back to your hand, net displacement would be = 0.
Which gives us -
Or, |v| = |u|.
Only the direction would change because first the ball was going up and now its coming down.
So, v = -29.4 m/s.
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