# Frictional force acting on mass

• demonslayer42
In summary, the question asks to find the frictional force acting on a 40 kg block sliding down a rough incline of 35 degrees with constant velocity. The solution involves using Newton's First Law to determine that the sum of forces along the incline is 0, and solving for the kinetic friction force, which is found to be 224.8 N acting up the incline and parallel to it.
demonslayer42

## Homework Statement

A 40 kg block slides down arough incline of 35 degrees with a constant velocity. Find the frictional force acting on the block.

## Homework Equations

Fgx = Fg sin theta
Fgy = Fg cos theta
Fg = mg

## The Attempt at a Solution

Well I drew a diagram and solved for my Fgx component and my Fgy component:

Fgx = 40(9.8)sin35 = 224.8 N
Fgy = 40(9.8)cos35 = 321.1 N

Now what do I do? Take the sum of Fx ? Won't that just be 224.8 N ? That doesn't sound correct I'm confused. Am I doing something wrong?

But I can't take the sum of Fx because I don't have an acceleration. I'm stuck :(

There is no acceleration along the incline, the acceleration is zero along the incline when the block is moving at constant velocity along the incline. Looks like Newton 1 applies.

That's what I was thinking, but if the a = 0 because it's at a constant velocity wouldn't that just mean the sum of my Fx would be 224.8 N ? So in this case Fx = fs ?Is this correct?

demonslayer42 said:
That's what I was thinking, but if the a = 0 because it's at a constant velocity wouldn't that just mean the sum of my Fx would be 224.8 N ?
the sum of your Forces in x direction (parallel to incline) would be 0 (no net force per Newton 1)!
So in this case Fx = fs ?Is this correct?
It's sum of forces (also called F_net) along incline = 0. Thus

mgsin theta (which is the component of the gravity force acting down the plane) - F_k (which is the kinetic friction force acting up the plane) = 0.

224.8 - F_k =0

F_k = 224.8 N acting up the incline and parallel to it.

Which i think it what you meant.

Yes, you are right that's what I meant. O.k., I think I'm starting to get the hang of this now thank you.

## 1. What is the definition of frictional force?

The frictional force is a contact force that opposes the motion of an object when it comes in contact with another object or surface.

## 2. How is the frictional force calculated?

The frictional force is calculated by multiplying the coefficient of friction (a value that represents the roughness of the surfaces in contact) by the normal force (the force exerted by an object on a surface).

## 3. How does the mass of an object affect the frictional force?

The mass of an object does not directly affect the frictional force. However, the weight of an object (which is determined by its mass) can affect the normal force and therefore affect the frictional force.

## 4. In what direction does the frictional force act?

The frictional force acts in the opposite direction of the object's motion or attempted motion. For example, if an object is sliding to the right, the frictional force will act to the left.

## 5. What are some real-life examples of frictional force acting on mass?

Some examples of frictional force acting on mass include a car's tires gripping the road to move forward, a person walking on the ground, and a book sliding across a table.

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