Work, Power, Energy, Efficiency

Click For Summary

Homework Help Overview

The discussion revolves around the concepts of work, power, energy, and efficiency, particularly focusing on the definition and application of work in a scenario involving gravitational forces and displacement.

Discussion Character

  • Conceptual clarification, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants explore the mathematical definition of work and its application to a specific problem involving displacement and gravitational force. Questions arise regarding the implications of displacement being zero in the context of an orbiting planet.

Discussion Status

The discussion is active, with participants examining different perspectives on the relationship between force, displacement, and work. Some guidance has been provided regarding the conditions under which work is considered to be zero.

Contextual Notes

There is an ongoing exploration of the assumptions related to gravitational forces and the nature of displacement in orbital motion. The original poster expresses uncertainty about the textbook answer, prompting further inquiry into the underlying concepts.

danielsmith123123
Messages
26
Reaction score
4
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?
 
Physics news on Phys.org
"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
 
  • Like
Likes   Reactions: russ_watters

Similar threads

Efficiency of a hydroelectric power station
  • · Replies 6 ·
Replies
6
Views
2K
Finding efficiency of an engine (with attempt)
  • · Replies 5 ·
Replies
5
Views
2K
DC Motor Efficiency: Why Does Efficiency Plot Look Like Parabola?
  • · Replies 3 ·
Replies
3
Views
2K
Long distance electrical transmission efficiency
  • · Replies 2 ·
Replies
2
Views
2K
Work done by power supply to maintain a constant current
  • · Replies 0 ·
Replies
0
Views
655
Avg Power in a Rotational Energy/Work Problem
  • · Replies 6 ·
Replies
6
Views
2K
Efficiency of Stirling Cycle - Is it the same as the Carnot Engine?
  • · Replies 14 ·
Replies
14
Views
2K
A Physics 11 Elevator Work/Power Problem
  • · Replies 3 ·
Replies
3
Views
4K
Efficiency and Temperature in Heat Engine Cycles: Approaching Parts B, C, and D
  • · Replies 1 ·
Replies
1
Views
1K
Conservation of Energy with springs
  • · Replies 13 ·
Replies
13
Views
1K