Working with Newton's Third Law and friction

In summary, when dealing with balanced or unbalanced forces, the basic equation is ΣF=ma, where a=0 in the balanced case. It is important to choose a direction and determine the components of the forces in that direction. Some common choices are vertical, horizontal, parallel to the plane, or normal to the plane. To solve the problem, you need to know how to calculate the components of a force in a given direction.
  • #1
ramseycharles0
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Homework Statement
If the mass (m) of the box is 20 kg and the ramp is 30 deg, what is the normal force (𝒏 ⃑)?
What is it’s acceleration down the ramp?
Relevant Equations
F=ma
I know that the normal force and Fg are unbalanced in this case, but I don't get how to set up the equilibrium equations with that. I struggle with determining what you set the equations equal to when its either balanced or unbalanced forces you're dealing with.
 

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  • #2
Do you know how to deal with vectors?
 
  • #3
ramseycharles0 said:
Homework Statement:: If the mass (m) of the box is 20 kg and the ramp is 30 deg, what is the normal force (𝒏 ⃑)?
What is it’s acceleration down the ramp?
Homework Equations:: F=ma

I know that the normal force and Fg are unbalanced in this case, but I don't get how to set up the equilibrium equations with that. I struggle with determining what you set the equations equal to when its either balanced or unbalanced forces you're dealing with.
Whether balanced or unbalanced, the basic equation is the same. In any direction you care to choose, the sum of force components in that direction determines the acceleration: ΣF=ma.
In the balanced case, a=0; that is the only difference.
So pick a direction. Usual choices are vertical, horizontal, parallel to the plane or normal to the plane.
Depending on exactly what you know and what you need to find, some choices may lead to a quicker solution than others, but you can always solve it by choosing any two of those four.
The key thing you need to be able to do is figure out the component of a given force in a given direction. Do you know how to do that?
 

1. How does Newton's Third Law apply to friction?

Newton's Third Law states that for every action, there is an equal and opposite reaction. This means that when an object is in contact with another object, it will experience a force in the opposite direction of the force it exerts on the other object. In the case of friction, when two surfaces rub against each other, the force of friction is equal and opposite on both surfaces.

2. How does friction affect motion according to Newton's Third Law?

Friction opposes motion, so when an object is in motion and experiences friction, the force of friction acts in the opposite direction of the object's motion. This results in a decrease in the object's speed, as the force of friction acts against the object's motion.

3. Can Newton's Third Law be used to calculate the force of friction?

Yes, Newton's Third Law can be used to calculate the force of friction. As mentioned before, the force of friction is equal and opposite on both surfaces in contact. By knowing the force exerted by one surface on the other, through Newton's Third Law, we can determine the force of friction.

4. How does the coefficient of friction affect Newton's Third Law?

The coefficient of friction is a measure of the amount of friction between two surfaces. It affects Newton's Third Law in that a higher coefficient of friction means a greater force of friction will be exerted between the two surfaces, as the surfaces have a stronger resistance to sliding against each other.

5. Can Newton's Third Law be applied to situations where there is no friction?

Yes, Newton's Third Law can still be applied to situations where there is no friction. In these cases, the force exerted by one object on another will still have an equal and opposite reaction, even if there is no friction between the two objects. This can be seen in situations like a person pushing a box on a frictionless surface, where the box will still experience a reaction force from the person's push.

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