Why Is Work Equal to Zero When Forces Are Perpendicular?

[xtrubambinoxpr]

Homework Statement

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.

Homework Equations

W=Kf-Ki

W=Fdcosθ

The Attempt at a Solution

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

 

[Doc Al]

See the picture attached please. I need help understanding the concept of why work is = 0.

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

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

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?

 

[xtrubambinoxpr]

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?

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

 

[1ndranil]

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

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.

 

[Nickie]

First of all, there are no silly questions when it comes to learning and understanding new concepts. It is important to ask questions in order to fully grasp a concept. So, do not worry about that.

Now, let's look at the basic energy problem. The concept of work is defined as the transfer of energy from one object to another by the application of a force. In this problem, we have an object being pushed to the left with a certain amount of force. However, the object does not move because there is an equal and opposite force acting on it, known as the normal force.

In this case, the normal force is acting perpendicular to the direction of the force pushing the object. This means that the work done by the normal force is zero, since the force and displacement are perpendicular to each other (cosθ=0). Therefore, the net work done on the object is also zero, as the work done by the force pushing the object is equal and opposite to the work done by the normal force.

To understand this concept better, you can think of it in terms of energy. The object has a certain amount of kinetic energy (Kf) before it is pushed. When the force is applied, it does not move, so its kinetic energy remains the same. This means that the work done by the force must be equal to the work done by the normal force, in order for the object's kinetic energy to remain constant.

I hope this helps to clarify the concept for you. If you still have any questions, please do not hesitate to ask.