# Basic Energy Problem (Concept)

1. Oct 27, 2013

### xtrubambinoxpr

1. The problem statement, all variables and given/known data

See the picture attached please. I need help understanding the concept of why work is = 0. I don't understand it's explanation. Please bare with me for the silly questions.

2. Relevant equations

W=Kf-Ki

W=Fdcosθ

3. The attempt at a solution

I cant understand why It mentions the normal force acting perpendicular if its being pushed to the left not up.

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• ###### Screen Shot 2013-10-27 at 4.33.57 PM.png
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2. Oct 27, 2013

### Staff: Mentor

The total work is zero, since the kinetic energy doesn't change. Look up the work-energy theorem.

The object is moving parallel to the the ramp, but the normal force acts perpendicular to it. So does the normal force do any work in this case?

3. Oct 27, 2013

### xtrubambinoxpr

You will have to dumb it down a good amount for me =/

4. Oct 28, 2013

### 1ndranil

If a particle moves on a frictionless rigid surface, due to the fact that this surface constrains the motion of the particle, we have an additional force acting (locally) perpendicularly to the surface.