Circular Motion Homework: Solving Part (B) & Understanding Centripetal Force

[haha1234]

Homework Statement

Homework Equations

The Attempt at a Solution

I have found the solution to part(B)
But I don't understand why the centripetal force is equal to the weight of the vehicle when the speed of the vehicle is maximum.

 

[xophergrunge]

But I don't understand why the centripetal force is equal to the weight of the vehicle when the speed of the vehicle is minimum.

Do you mean maximum? The minimum speed would be zero.

 

[haha1234]

Do you mean maximum? The minimum speed would be zero.

Yes.Sorry for my typo

 

[xophergrunge]

Okay. So, what would happen if the centripetal force became greater than the weight?

 

[Doc Al]

But I don't understand why the centripetal force is equal to the weight of the vehicle when the speed of the vehicle is maximum.

What are the only forces acting on the vehicle?

 

[haha1234]

Okay. So, what would happen if the centripetal force became greater than the weight?

I don't know

 

[haha1234]

What are the only forces acting on the vehicle?

Centripetal force and tangential force?

 

[Doc Al]

Centripetal force and tangential force?

No, I'm talking about real forces. ("Centripetal force" is just the name given to whatever force is producing the centripetal acceleration. It's not a kind of force.)

Hint: One of those forces is gravity. What's the other? (I'm only interesting in forces that act at the top of the motion.)

 

[haha1234]

No, I'm talking about real forces. ("Centripetal force" is just the name given to whatever force is producing the centripetal acceleration. It's not a kind of force.)

Hint: One of those forces is gravity. What's the other? (I'm only interesting in forces that act at the top of the motion.)

Normal force? But I don't know how they are relevant to the maximum speed

 

[Doc Al]

Normal force?

Yes!

But I don't know how they are relevant to the maximum speed

They are relevant because those two forces combine to give you the centripetal force.

What direction do those forces act? Express the centripetal force in terms of those forces.

The force of gravity cannot change, but what about the normal force?

 

[haha1234]

Yes!


They are relevant because those two forces combine to give you the centripetal force.

What direction do those forces act? Express the centripetal force in terms of those forces.

The force of gravity cannot change, but what about the normal force?

Am I correct?
But when the centripetal force is greater than the weight, the normal force will be smaller than zero.
Is it correct?

 

[Doc Al]

Am I correct?
But when the centripetal force is greater than the weight, the normal force will be smaller than zero.
Is it correct?

Yes.

Of course the normal force cannot be less than zero. What will happen is that the vehicle will leave the track if the speed is too great. The point where it is going as fast as it can and still maintain contact will be when the normal force goes to zero.

 

[haha1234]

Yes.

Of course the normal force cannot be less than zero. What will happen is that the vehicle will leave the track if the speed is too great. The point where it is going as fast as it can and still maintain contact will be when the normal force goes to zero.

Why the vehicle will leave the track when the normal force becomes zero?
Sorry for my stupidity.:shy:

 

[Doc Al]

Why the vehicle will leave the track when the normal force becomes zero?

As long as the vehicle is pressing against the track there will be a normal force. When the normal force goes to zero, that means it is no longer pressing against the track--if it goes any faster, it begins to go flying off.