Work Force Questions: Explaining Why Work Done is Zero

In summary: The static friction force does not do any work because it is in the opposite direction as the displacement.
  • #1
parwana
182
0
In most circumstances, the normal force acting on an object and the force of static friction do no work on the object. However, the reason that the work is zero is different for the two cases. In each case, explain why the work done by the force is zero.
 
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  • #2
Look at the definition of work. What does the work equal if the force and displacement are perpendicular?
 
  • #3
W= Fx

Thats work. But there also can be an angle between them
 
  • #4
Yes but what is the relation? What happens when that angle is 90 degrees?
 
  • #5
parwana said:
W= Fx

Thats work. But there also can be an angle between them

Yes, that's work when the angle between the vectors F (the force) and x (the displacement) equals zero. But, when the angle is non zero, as in your case, the work is given with W = F x cos(angle). Now, as rfk asked, what happens when the angle equals 90 degrees?
 
  • #6
work will be zero
 
  • #7
can anyone help and explain in detail
 
  • #8
parwana said:
can anyone help and explain in detail
You have already I think determined from the help of the responders that the work is zero when the displacement is 90 degrees to the force. Generally the normal force is 90 degrees to the displacemnt vector, so it does no work. Like when you push a block along a level table, the normal force between the block and table acts straight up on the block, and the block moves perpendicularly to it (to the right). so the normal force does no work (W=Ndcos90 = 0). But you still have another question to answer. Why does the static friction force generally not do any work? It's for a different reason.
 
  • #9
^ that's what I don't get, why doesn't static friction not do any work. Usually friction is in the opposite direction as the movement right. Now how can that make it not work?
 
  • #10
parwana said:
^ that's what I don't get, why doesn't static friction not do any work. Usually friction is in the opposite direction as the movement right. Now how can that make it not work?
What does static mean?
 
  • #11
parwana said:
^ that's what I don't get, why doesn't static friction not do any work. Usually friction is in the opposite direction as the movement right. Now how can that make it not work?
When an object is moving, it is subject to kinetic friction, not static friction. Kinetic friction does lots of work, since the kinetic friction force is in the same direction of the displacement.. But what can you say about static friction force and displacemnt?
 

Related to Work Force Questions: Explaining Why Work Done is Zero

What is work force?

Work force refers to the amount of effort or energy that is exerted by individuals or machines to produce a desired output or complete a task.

What is the formula for calculating work force?

The formula for calculating work force is W = F x d, where W is the work done, F is the force applied, and d is the distance over which the force is applied.

What does it mean when work done is zero?

When work done is zero, it means that there is no movement or displacement of an object. This can occur when the force applied is perpendicular to the direction of motion, or when there is no force applied at all.

What are some real-life examples of work done being zero?

Some examples of work done being zero include pushing against a wall, carrying a book while walking on a level surface, and lifting a weight at a constant height.

Why is it important to understand why work done is zero?

Understanding why work done is zero can help us identify and troubleshoot problems in systems or processes. It also allows us to optimize our use of energy and resources by minimizing unnecessary work.

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