Physics Question

Factual Questions
1

Hey,
I’ve got this physics problem and I can’t solve it…
So for all those physics people out there have fun

Ok here is what I know:
A ball is attached to a string with length of L. It swings in a horizontal circle, with a constant speed. The string makes an angle (theta) with the vertical, and T is the magnitude of the tension in the string.

Determine the Mass of the Ball.
Determine th Speed of the Ball.
Determine the Frequency of revolutions of the Ball.
Suppose the strings breaks as the ball swings in its circular path. Describe the trajectory of the ball after the strings breaks but before it hits the ground.

Good luck.

2

ohh yeah the string is attached to a fixed point

3

Um, is this a homework problem or class assignment of some kind?

4

Is that a problem?

Its only one little part of it?
I really want to know how to do it so if anyone could help that would be great

5

Alright forget it guys…don’t feel obligated to answer this
It shoudl not have been posted here
Only answer this is you are in love with physics or somehting
Moderator u can destroy this if you want

6

I’d recommend you get help from your teacher. However, I was just recently in your situation and can sympathise. Unfortunately, I don’t know how to do the question. :o

7

If this is your homework, I won’t answer the question, but I will give some leading questions that might help you:
[ul]
[li]How do you relate tension to force?[/li][li]What is the total force on the ball?[/li][li]What is the easiest coordinate system (spherical, cylindrical, euclidean) to break the total force up into its parts?[/li][/ul]

8

I won’t tell you the answer but I can give some hints.

  1. Look at the ball as if it were frozen in space.

  2. Break up the various forces into components.

  3. You know what the motion is, so you can set up a force balance and solve for whatever you need.

9

Because of my website, I constantly receive email from students wanting me to do their homework for them.

One solution (if the homework problem is interesting) is to wait a few days or a week, and THEN answer it. If it wasn’t homework, then the person is satisfied. If it WAS homework, then perhaps my answer coming in after the papers were handed back helps that student in learning physics.

Doesn’t work so well in SDMB thought.

10

Suppose the strings breaks as the ball swings in its circular path. Describe the trajectory of the ball after the strings breaks but before it hits the ground.

Here’s another hint. You can answer this part without knowing anything about the ball’s previous motion, other than it is travelling in a horizontal plane at a certain tangential velocity.

11

what’s the big deal in helping a kid out with his homework?..isn’t the point of homework to help you learn the material so you do well on the test?..if he’s just looking for easy credit and doesn’t care about learning the material then he won’t do well on the exam and will learn his lesson.

12

Well, the big deal in my mind is: does the kid care about learning the material? Why should I spend time explaining a concept when the person asking doesn’t care about the explanation, but just wants the answer to score an extra HW point?

So if I see a question that’s obviously a homework problem, and is just repeated verbatim without commentary (especially if it’s not acknowledged as a HW problem), I’m unenthusiastic about replying. If, on the other hand, I see some indication that the OP has put some thought into the problem and needs some guidance (like, “hey, we did this in class, and I don’t see how it applies,” or “I got this far, but the answer doesn’t make sense to me, and I can’t figure out where I made an error”) then helping a kid out with his homework isn’t such a big deal.

To the OP: Draw a free body diagram. If you don’t know what a free body diagram is, complain to your teacher.

13

Say the ball has mass M and moves at speed v.

The forces that act on the ball are weight (Mg) and the tension of the string (T). The ball has a constant angular velocity (w=v/r where r=L sin theta) and thus no angular acceleration.

Since the ball moves in a horiozontal circle, it doesn’t move up or down. Thus, forces in the down direction (Mg) and up direction (T cos theta) are equal. You can calculate the mass. That should get you started.