What is the frictional force at constant velocity?

In summary, you are trying to determine the magnitude and direction of the frictional force between two masses when one mass is moved horizontally and a force is applied from the left. The forces involved are weight (down), normal reaction force (up), and the applied force (to the right). The friction force is to the left.
  • #1
moonbase
21
0

Homework Statement


A 10 N force is horizontally applied to a cart from the left. The cart moves to the right with a constant velocity. What is the magnitude and direction of the frictional force? (In terms of mass)

Homework Equations


Fnet=ma
fk=ukN

The Attempt at a Solution


I know Newton's second law shouldn't apply since the acceleration equals zero so there is no net force. But I'm confused as to how I can get all the forces to cancel out if the applied force needs to be greater than the frictional force in order for the cart to move. So the frictional force can't be 10 N. Is there a force I'm missing or is there something wrong with my reasoning?
 
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  • #2
moonbase said:

Homework Statement


A 10 N force is horizontally applied to a cart from the left. The cart moves to the right with a constant velocity. What is the magnitude and direction of the frictional force? (In terms of mass)

Homework Equations


Fnet=ma
fk=ukN

The Attempt at a Solution


I know Newton's second law shouldn't apply since the acceleration equals zero so there is no net force. But I'm confused as to how I can get all the forces to cancel out if the applied force needs to be greater than the frictional force in order for the cart to move. So the frictional force can't be 10 N. Is there are force I'm missing or is there something wrong with my reasoning?

your problem lies in the statement in red, above.

You do, and have, used Newton's second law when you concluded "... so there is no net force".

getting all the forces to cancel out is easy ...

Weight down
Normal Reaction Force up
Applied Force to the right [applied from the left]
Friction Force to the left.

They cancel in pairs.
 
  • #3
Oh okay, I was getting static and kinetic friction mixed up. Thanks
 

Related to What is the frictional force at constant velocity?

1. What is friction at constant velocity?

Friction at constant velocity, also known as kinetic friction, is the resistance or force that opposes the motion of an object when it is moving at a constant speed.

2. What factors affect friction at constant velocity?

The amount of friction at constant velocity is affected by the type of surfaces in contact, the force pushing the surfaces together, and the smoothness of the surfaces.

3. How is friction at constant velocity different from static friction?

Static friction is the resistance or force that must be overcome in order to start an object in motion, whereas friction at constant velocity is the resistance that acts on an object that is already in motion.

4. How can friction at constant velocity be reduced?

Friction at constant velocity can be reduced by using lubricants, such as oil or grease, between the surfaces in contact. It can also be reduced by using smoother materials for the surfaces or by reducing the force pushing the surfaces together.

5. What are some real-life examples of friction at constant velocity?

Examples of friction at constant velocity include the movement of a car on a road, the sliding of a book on a table, or the rolling of a ball on a surface. In these cases, the objects are moving at a constant speed and are experiencing friction from the surfaces they are in contact with.

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