# Uniform Circular Motion and centripetal force

• BlueEight
In summary, the conversation discusses an experiment in a physics class involving a stopper attached to a string and a weight. The attempt at a solution considers the possibility of the stopper not being held up by adequate centripetal force and the concept of a horizontal circle not being physically possible. It is concluded that the mass will not stay in a horizontal circle and that this information may be necessary for experimental precision.
BlueEight

## Homework Statement

http://img.skitch.com/20091201-pxecs3d574itggpejybhdbp3qr.jpg

Essentially, as an experiment, our physics class whirled a stopper attached to a string that went through a tube that was finally attached to a weight on the bottom of the string.

## The Attempt at a Solution

I'm not really sure, unless the centripetal force is somehow not adequate to hold the weight up, but it should be, as long as the stopper is swung around quickly enough.. This seems contradictory to everything that we've learned about UCM this semester.

I think you need to show that a horizontal circle as show in the diagram is not physically possible?

Oh yeah! Because if it was horizontal, there would be no "vertical tension" holding up the mass of the stopper?

BlueEight said:
Oh yeah! Because if it was horizontal, there would be no "vertical tension" holding up the mass of the stopper?
yes

Tsinθ=mg, θ=0, the mass will not stay in a horizontal circle.

Ah, thanks. But why would it be "necessary for experimental precision?"

## 1. What is uniform circular motion?

Uniform circular motion is the motion of an object in a circular path at a constant speed, where the direction of motion is constantly changing.

## 2. How is centripetal force related to uniform circular motion?

Centripetal force is the force that causes an object to move in a circular path. In uniform circular motion, the centripetal force is directed towards the center of the circle and is responsible for keeping the object moving along the circular path.

## 3. What is the formula for calculating centripetal force?

The formula for calculating centripetal force is F = (mv^2)/r, where F is the centripetal force, m is the mass of the object, v is the velocity, and r is the radius of the circular path.

## 4. Can uniform circular motion occur without centripetal force?

No, uniform circular motion cannot occur without centripetal force. In order for an object to move in a circular path at a constant speed, there must be a force acting towards the center of the circle to keep the object from moving in a straight line.

## 5. How does changing the speed or radius affect centripetal force in uniform circular motion?

If the speed of the object increases, the centripetal force also increases. If the radius of the circular path increases, the centripetal force decreases. This is because the centripetal force is directly proportional to the square of the speed and inversely proportional to the radius.

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