1. Suppose you pull up on an 8.5 kg bowling ball to lift it through a distance o
ID: 1458373 • Letter: 1
Question
1. Suppose you pull up on an 8.5 kg bowling ball to lift it through a distance of 2.0 m at a constant velocity.
What is the work done by the external lifting force you apply? (Is the work done by you positive or negative?
Is the (overall) work positive or negative? Show your calculations. Hint: What is the magnitude of the gravitational force you must counterbalance?
Possible ans mgd=(8.5kg)(9.8m/s)(2.0m)= +167J-(you) overall is negative -167J? (Check my work)
2. Recall that you lifted the 8.5 kg bowling ball through a distance of 2.0 m at a constant velocity.
What is the net force on the ball in that case?
What is the net work on the ball while it is being lifted? (Is the net work positive, negative, or zero? Show your calculations.)
Possible ans: -167J? Net work = +167J-167J=0 (Check my work)
3. Imagine that you let go of the bowling ball so it falls freely for a distance of 1.0 m.
What is the work associated with the gravitational force that the Earth exerts on the ball while it is falling?
Is work done by the gravitational force in the same direction or in the opposite direction to the displacement? (Is the work positive or negative? Show your calculations.)
Possible ans: mgh (8.5kg)(9.8)(1m) = 83.3J (Check my work)
Explanation / Answer
given,
mass = 8.5 kg
distance = 2 m
work done by the person lifting the ball = mgh
work done by the person lifting the ball = 8.5 * 9.8 * 2
work done by the person lifting the ball = 166.6 J
overall work done is 0 since work done by gravity is -166.6 J as direction of motion is opposite direction of force
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