Work on an object moving downards

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When moving a textbook from a high shelf to a low shelf, the work done is negative because the force exerted by the person is upward while the motion of the textbook is downward. This results in the force and displacement being in opposite directions, leading to a negative work calculation. The equation W = Fcosd indicates that when the angle θ is 180 degrees, work is negative. The initial confusion stemmed from misinterpreting the direction of the force relative to the motion. Understanding this concept clarifies the nature of work in physics.
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Homework Statement


You move a textbook from a high shelf to a low shelf. Is the work you do on it positive or negative?

Homework Equations


W = Fcosd

The Attempt at a Solution


My understanding is that if you are doing a positive applied force on the textbook, over some distance, the work should be positive. But the answer is negative. Why?
 
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In what direction is the force YOU exert? Compare this with the direction of motion.
 
brainpushups said:
In what direction is the force YOU exert? Compare this with the direction of motion.
The motion is upwards, the direction is downwards.
 
AAAA said:
upwards

That's not how you phrased the question:

AAAA said:
You move a textbook from a high shelf to a low shelf. Is the work you do on it positive or negative?

From a high to a low shelf means the motion is downward. The force you exert is upward. Therefore the work you do is negative (force and displacement are in the opposite direction i.e. θ = 180)
 
brainpushups said:
That's not how you phrased the question:
From a high to a low shelf means the motion is downward. The force you exert is upward. Therefore the work you do is negative (force and displacement are in the opposite direction i.e. θ = 180)

Right, sorry! I meant the force is upwards. Yes, I understand now. Thanks!
 
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