1) When answering the questions below, consider whether the applied force is par
ID: 1459880 • Letter: 1
Question
1) When answering the questions below, consider whether the applied force is parallel to the displacement of the book. a.) Lift a book from the floor to the table at constant speed. Did you do work? Why or why not? If so, was the work you did positive or negative? b.) Consider the same case as Part (a). Does gravity do work on the book? Why or why not? If so, was the work gravity did positive or negative? c.) What if you carry the book horizontally as you walk across the floor at constant speed? Did you do work then? Why or why not? If so, was the work you did positive or negative? d.) How does your answer to Part (c) change if your speed increases? Decreases?
2) Draw a force diagram for the book that is lifted vertically at a constant velocity. On this force diagram, show the forces acting on the book. Mark the relative lengths of the vectors correctly – bigger forces should have longer force vectors. What was the average lifting force acting on a 1 kg book as it was lifted at a constant velocity? Could you lift the book with a constant force? Ignore the very beginning and end of the motion in answering the question.
Explanation / Answer
if we lift a book from the floor we apply upward force that is in the direction of the motion of the book so work is done by us and since the motion is in the direction of the force work done will be positive
yes gravity also does work and since the speed is constant net vertical force on the book will be 0 so will be the net work so gravity will do negative work of same amount so as to mage net work done 0
if we carry a book horizontally with constant speed so net force will be 0 as speed is constant and so work wdone will also be 0
if speed decreasses or increases this will produce some acceleration and hence some force and work done will be positive if speed is increasing and negative is speed is decreasing
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