Why Is Frictional Force Less Than Weight on an Inclined Plane?

In summary, the frictional force acting on the block at rest on an inclined plane with a rough surface is less than the weight of the block. This is because the force of static friction must be equal to the component of weight parallel to the incline, and not the full weight.
  • #1
StephenDoty
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0
If a block is at rest on an inclined plane with a rough surface, what is the frictional force compared to the weight of the block?

Well if the block is at rest that means that the frictional force is the static frictional force, and since the block is not moving shouldn't the static frictional force be greater than the weight of the block?

According to my professor the correct answer is that the frictional force acting on the block is less than the weight of the block. WHY?

Even if the force is kinetic frictional force, since the block is not moving shouldn't the frictional force be equal to the weight of the block?

Thank you.

Stephen
 
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  • #2
If the block is at rest--in equilibrium--what must be the net force on it? Analyze the forces on the block that act parallel to the incline. (One of those forces is friction. What's the other?)
 
  • #3
weight equaling mgsin(theta)

so using Newton's laws shouldn't the fictional force equal the weight?

Why is the correct answer that the fictional force is less than the weight?
 
  • #4
StephenDoty said:
weight equaling mgsin(theta)
That's the component of the weight parallel to the incline. The weight itself is mg.

so using Newton's laws shouldn't the fictional force equal the weight?
The net force must be zero, thus the friction force must equal that component of the weight.

Why is the correct answer that the fictional force is less than the weight?
If friction = mg sin(theta), how must it compare to the full weight (mg)? :wink:
 
  • #5
since it is at rest, and static frictional force varies, the weight downwards only the inclined plane equals the frictional force, and will remain to equal it, until the maximum static friction is reached then it jerks loose
 

Related to Why Is Frictional Force Less Than Weight on an Inclined Plane?

1. What is the difference between force and friction?

Force is a push or pull that causes an object to accelerate or change its motion. Friction is a force that opposes motion and can result in the slowing down or stopping of an object.

2. How does friction affect the movement of objects?

Friction acts in the opposite direction of an object's motion, causing it to slow down or stop. It also affects the amount of force needed to move an object.

3. What factors affect the amount of friction between two surfaces?

The amount of friction between two surfaces depends on the types of surfaces involved, the force pressing the surfaces together, and the roughness of the surfaces.

4. How can friction be reduced?

Friction can be reduced by using lubricants, such as oil or grease, between two surfaces or by using smoother surfaces.

5. How is friction important in everyday life?

Friction plays an important role in everyday life. It allows us to grip objects, walk without slipping, and control the speed of vehicles. It also helps us to write, use tools, and perform other tasks that require friction for traction and control.

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