Work, Power, Energy, Efficiency

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SUMMARY

The discussion centers on the concept of work in physics, specifically defined by the equation W = Fd, where W represents work, F is force, and d is displacement. The participants clarify that if the displacement is zero, as in the case of Planet X orbiting the moon, the work done is also zero. This is due to the requirement that force and displacement must be in the same direction for work to be performed. The conversation emphasizes the importance of understanding the relationship between force, displacement, and the direction of motion in calculating work.

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danielsmith123123
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Homework Statement
Calculate the work done by planet X on its moon.
Planet X applies a force of 5.6 x 10^10 N on its moon and the moon is 4.0 x 10^8 km away from the planet and it continues to circle the planet in a circular orbit of circumference of 2.5 x 10^9 m.
Relevant Equations
Gravity
The answer in the textbook says 0J but I am not sure what the concept behind it is. Does it have something to do with gravity?
 
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"Gravity" is not an equation. What is the mathematical definition (equation) of work?
 
russ_watters said:
"Gravity" is not an equation. What is the mathematical definition (equation) of work?
W = fd
 
danielsmith123123 said:
W = fd
Great, so can you apply it to this problem?
 
russ_watters said:
Great, so can you apply it to this problem?
W = Fd -------------- W = (5.6 x 10^10 N) (d) Would "d" be 0 because Planet X keeps orbiting the moon and essentially coming back to where it initially started therefore making it's displacement 0?
 
danielsmith123123 said:
W = Fd -------------- W = (5.6 x 10^10 N) (d) Would "d" be 0 because Planet X keeps orbiting the moon and essentially coming back to where it initially started therefore making it's displacement 0?
Yep, that's one way to look at it - the other is along the direction of motion there is no force. Essentially, the force and displacement have to be in the same direction. Since you don't have that, they'll multiply to zero.
 
russ_watters said:
Yep, that's one way to look at it - the other is along the direction of motion there is no force. Essentially, the force and displacement have to be in the same direction. Since you don't have that, they'll multiply to zero.
Ok, thank you so much
 
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