# Trouble be force diagram, verticle circle

• jegues
In summary, the person attempted to solve a force diagram issue by drawing a right angle triangle with the hypothenuse as mg. However, they realized their mistake after drawing the triangle and found that h should be the shorter side and not mg.
jegues
Hello all,

I seem to be having issues drawing the correct force diagrams... The question is as follows:

"A 1kg mass, attached to the end of a string, is swung in a vertical circle having radius of 0.3m. When the string makes and angle of 30 degrees below horizontal, the speed of the mass is 3.0m/s.

My attempt at the solution (I know the force diagram is where I'm going wrong) is in the picture along with my drawn diagram. (It's attached to this thread)

Note: phi is simply 90-30 = 60 degrees. I also forgot to put a dash inbetween mg and sin(theta)

It should look like this:

T - mg/sin(theta) = ma
T = m[(v^2)/r] + mg/sin(theta)

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• DiagramQuestion.JPG
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jegues said:
Hello all,

I seem to be having issues drawing the correct force diagrams... The question is as follows:

"A 1kg mass, attached to the end of a string, is swung in a vertical circle having radius of 0.3m. When the string makes and angle of 30 degrees below horizontal, the speed of the mass is 3.0m/s.

My attempt at the solution (I know the force diagram is where I'm going wrong) is in the picture along with my drawn diagram. (It's attached to this thread)

Note: phi is simply 90-30 = 60 degrees. I also forgot to put a dash inbetween mg and sin(theta)

It should look like this:

T - mg/sin(theta) = ma
T = m[(v^2)/r] + mg/sin(theta)

Hi there

It is the triangle you drew with mg and h that is incorrect. You drew it with h being the hypothenuse.

But it is the force mg which should be the hypothenuse of your right angle triangle. h should be a shorter side (one of the shorter sides will be tangent to the circle and the other short side will be parallel with the radius)

By the way, what software did you use for your drawing? I am just curious.

Thank you! I knew my mistake wasn't in the mg triangle I just couldn't see how to repair it!

I used an online whiteboard to make my drawings. (www.scriblink.com[/URL])

Last edited by a moderator:
jegues said:
Thank you! I knew my mistake wasn't in the mg triangle I just couldn't see how to repair it!

I used an online whiteboard to make my drawings. (www.scriblink.com[/URL])[/QUOTE]

You are welcome!

And thank you for the link!

Regards

Last edited by a moderator:

## 1. What is a force diagram in relation to a vertical circle?

A force diagram is a visual representation of all the forces acting on an object in a specific situation, such as a vertical circle. It helps to analyze and understand the forces involved in the motion of the object.

## 2. What are the main forces present in a vertical circle?

The main forces present in a vertical circle are the centripetal force, which acts towards the center of the circle, and the weight of the object, which acts downwards towards the center of the Earth.

## 3. How does the force diagram change at different points in a vertical circle?

At the top of the circle, the centripetal force is greater than the weight, causing the object to accelerate downwards. At the bottom of the circle, the weight is greater than the centripetal force, causing the object to accelerate upwards. At the sides, the centripetal force and weight are equal, resulting in a constant speed.

## 4. How does the mass of the object affect the force diagram in a vertical circle?

The mass of the object affects the force diagram in a vertical circle by influencing the magnitude of the centripetal force required to keep the object moving in a circular path. A heavier object will require a greater centripetal force to overcome its weight and maintain its motion in the circle.

## 5. Can the force diagram in a vertical circle be used to determine the speed of the object?

Yes, the force diagram in a vertical circle can be used to determine the speed of the object. By analyzing the forces present and using Newton's second law of motion, the speed of the object can be calculated at any point in the circle.

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