# Constraint forces on a circle

when a particle is constraint to move on a circle, what are the constraint forces

when a particle is constraint to move on a circle, what are the constraint forces

What is the particle?

What forces do you know that can act on particles?
Could any of these provide a 'central force'?

HallsofIvy
Homework Helper
This depends upon HOW the particle is constrained to move in a circle. If the particle is attached to a circular track, the answer is obvious. If the particle is an electron going around a positive charge, the answer is also obvious but not the same as before.

Frankly, this looks like a question at the end of a chapter of a basic science text- where they are really testing whether you have read the chapter!

tiny-tim
Homework Helper
when a particle is constraint to move on a circle, what are the constraint forces

usljoo, you know the procedure by now …

you tell us what you think the answer is,

and then we comment! ok look at the attachment

#### Attachments

• circle eqa.doc
131.5 KB · Views: 158
tiny-tim
Homework Helper
my mac doesn't do .doc

how long can it be? can't you find the time to type it out for us? i hope ur mac does pdf :P

#### Attachments

• circle eqa.pdf
62.8 KB · Views: 155
tiny-tim
Homework Helper
i don't understand what your .pdf has to do with the question when a particle is constraint to move on a circle, what are the constraint forces

And this is the reason why it is harder to apply a force like on the picture to a circle of smaller radius and that is because there will be a component of the centripetal force that is opposite to the applied force F on the picture and that’s why torque gets smaller with r.

There is no way that F has anything to do with motion around the circle you have drawn.

None of this is meant as a personal criticism; I really am trying to help.

You did not bother to answer my previous question. All my questions are designed to help and further understanding.

Have a look at this recent thread, where I like to think the OP went away with a better understanding and achieved something for himself.

Now just answer this simple question.

If you take a string and pull it out taught so it is under tension, what are the forces acting in the string and on the string?
Can you draw a simple diagram?

There is no way that F has anything to do with motion around the circle you have drawn.

None of this is meant as a personal criticism; I really am trying to help.

You did not bother to answer my previous question. All my questions are designed to help and further understanding.

Have a look at this recent thread, where I like to think the OP went away with a better understanding and achieved something for himself.

Now just answer this simple question.

If you take a string and pull it out taught so it is under tension, what are the forces acting in the string and on the string?
Can you draw a simple diagram?

the forces on the string are the tension force witch acts on the pivot where you binded the string and the same acts also on your hand but i dont see what this has anything to do witch my question

im asking you under these constraints that i have drawn and when you apply a tangential force F as shown what are the forces of the constraint and how will they affect my force F

the forces on the string are the tension force witch acts on the pivot

This doesn't make sense. Is the force acting on the string or the pivot? I actually asked about the string.

You really need to pay attention to what is said.

Did you draw a diagram?

And, yes, the question has direct relevance, which will become clear.

well look man i really am no beginner here and the question is far from trivial so dont ask me these questions about the string because you didnt get my question i think better tell me what the forces of constraints are

go well