How Can Kinetic Energy Change with Zero Net Work?

Click For Summary

Homework Help Overview

The discussion revolves around the work-energy theorem, specifically addressing the scenario of a box being pushed on a horizontal surface with a constant velocity. Participants are exploring the apparent contradiction between the change in kinetic energy and the concept of zero net work when frictional forces balance the applied force.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants are questioning how kinetic energy can change despite the net work being zero, particularly focusing on the transition from rest to constant velocity. There is a discussion about the forces involved, including static and kinetic friction, and the implications of these forces on work done.

Discussion Status

The discussion is active, with participants raising questions about the assumptions underlying the work-energy theorem. Some have pointed out that the total work cannot be considered zero during the transition to constant velocity, indicating a productive exploration of the topic.

Contextual Notes

There is mention of the coefficient of static friction being greater than that of kinetic friction, which may influence the forces at play during the initial movement of the box. Participants are examining the implications of these frictional forces on the overall work done.

madah12
Messages
326
Reaction score
1

Homework Statement


There is something I don't understand in work energy theorem
If we push on a box on a horizontal surface with force F to cause it to move with displacement x with constant velocity that means the force by friction is equal to F right? so the total work is the net force times the displacement which is zero
but the box was initially at rest then it is moving with constant velocity so there is change in kinetic energy
so how can there be change in kinetic energy with zero work?


Homework Equations





The Attempt at a Solution

 
Physics news on Phys.org
when the body is moving with constant velocity, there is no change in constant velocity.

Also, for the body to start from rest, it needs a little more force (if you notice that coefficient of static friction is more than kinetic)...
 
Then in the time interval from just before you applied the force till it moved with constant velocity we can't actually say the total work is 0 right?
 
exactly.
 

Similar threads

Replies
1
Views
2K
Replies
1
Views
2K
  • · Replies 8 ·
Replies
8
Views
2K
Replies
3
Views
2K
  • · Replies 33 ·
2
Replies
33
Views
4K
Replies
8
Views
3K
  • · Replies 56 ·
2
Replies
56
Views
5K
  • · Replies 7 ·
Replies
7
Views
1K
  • · Replies 10 ·
Replies
10
Views
2K