SOLUTION: A boy tosses a coin upward with a velocity of +14.7m/s. Find
(a) the maximum height reached by the coin,
(b) time of flight, and the
(c) velocity when the coin returns to the
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(a) the maximum height reached by the coin,
(b) time of flight, and the
(c) velocity when the coin returns to the
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Question 1180996: A boy tosses a coin upward with a velocity of +14.7m/s. Find
(a) the maximum height reached by the coin,
(b) time of flight, and the
(c) velocity when the coin returns to the hand.
(d) Suppose the boy failed to catch the coin and the coin goes to the
ground, with what velocity will it strike the ground? The boy's hand is
0.49m above the ground. Found 2 solutions by ikleyn, Edwin McCravy:Answer by ikleyn(52814) (Show Source):
I will answer all questions as if they came from Physics.
(a) Use the Law of conservation of mechanical energy.
mgh = ,
where m is the mass of the coin.
Cancel the factor m in both sides and express the maximum height
= = = 11 meters (rounded) above the starting height.
(b) Time of flight to the upper point
= = = 1.5 seconds (rounded).
The total time to fly up and to return to the starting height = = 3 seconds (rounded).
(c) Velocity when the coin returns to the hand = staring velocity = 14.7 m/s
due to the Mechanical energy conservation Law.
(d) Apply the Mechanical energy conservation Law again with the changed value of the final height.
I think you should use the four standard equations of motion, and be careful
that upward vector quantities are positive and downward ones are negative.
The tutor above failed to observe this convention.
A boy tosses a coin upward with a velocity of +14.7m/s. Find
(a) the maximum height reached by the coin,
Answer: 11.515 m
(b) time of flight
Answer: 3 seconds.
(c) velocity when the coin returns to the hand. (The boy's hand is 0.49m above
the ground.)
That's the velocity that's equal in magnitude but opposite in direction
velocity as the velocity when it left his hand.
Answer: -14.7 m/s
(d) Suppose the boy failed to catch the coin and the coin goes to the ground,
with what velocity will it strike the ground?
We take the negative square root because the final velocity is downward.
Answer: -15.02 m/s
Edwin
