# Circular Motion: Find Speed at Point A

• Bryan Tran
In summary, the problem involves a 0.8 kg lead ball on a string being whirled at a length of 5 meters. At the top of the circle, the tension in the string is 4.96 N and the speed of the ball is 5.57 m/s. The forces acting on the ball include the weight and another force, and a free body diagram may be helpful in solving the problem.
Bryan Tran

## Homework Statement

A .8 kg lead ball is whirled on the end of a string 5 meters long. When the ball passes through point A at the top of the path, the tension in the string is 4.96 N.
What is the speed of the bob at point A?
*NOTE - POINT A is at the top of the circle...

F=ma
F=m(v2/r)

## The Attempt at a Solution

F=m(v2/r)
v = √(F*r)/m

V = √(4.96*5)/.8
V = 5.57 m/s

DOESN'T WORK...!

At the top of the circle, what are the forces acting and in what directions do they act (up or down) ?

The resultant of these forces is equal to the centripetal force mv2/r

Umm force of weight and that's all... and it acts down.
But what does that do?

Bryan Tran said:
Umm force of weight and that's all... and it acts down.
But what does that do?

Not just weight. Another force acts on it too. You've mentioned it in the problem itself.

Bryan Tran said:
Umm force of weight and that's all... and it acts down.
But what does that do?
Have you drawn a free body diagram showing the forces acting on the ball, or do you feel you have advanced beyond the point where you need to use free body diagrams?

## 1. What is circular motion?

Circular motion is the movement of an object along a circular path, where the distance from the center of the circle remains constant.

## 2. How is speed calculated in circular motion?

The speed at any point in a circular motion can be calculated by dividing the circumference of the circle by the time it takes to complete one full revolution.

## 3. What is the difference between linear speed and angular speed?

Linear speed refers to the distance an object travels in a given amount of time, while angular speed refers to the rate of change of the angle of rotation of an object in circular motion.

## 4. How does the radius of the circle affect the speed at point A?

The speed at point A in circular motion is directly proportional to the radius of the circle. This means that a larger radius will result in a higher speed at point A, and a smaller radius will result in a lower speed at point A.

## 5. Can the speed at point A be greater than the average speed in circular motion?

Yes, the speed at point A can be greater than the average speed in circular motion. This occurs when the object is moving faster at point A compared to other points along the circular path.

• Introductory Physics Homework Help
Replies
2
Views
698
• Introductory Physics Homework Help
Replies
8
Views
1K
• Introductory Physics Homework Help
Replies
14
Views
2K
• Introductory Physics Homework Help
Replies
9
Views
2K
• Introductory Physics Homework Help
Replies
5
Views
1K
• Introductory Physics Homework Help
Replies
4
Views
1K
• Introductory Physics Homework Help
Replies
3
Views
2K
• Introductory Physics Homework Help
Replies
7
Views
2K
• Introductory Physics Homework Help
Replies
5
Views
315
• Introductory Physics Homework Help
Replies
4
Views
1K