What could be causing the discrepancy in my circular motion calculations?

[PianoMan]

God, I'm getting so frustrated.

A 0.50kg ball that is tied to the end of a 1.5m light cord is revolved in a horizontal plane with the cord making a 30 degree angle with the vertical.

a) what is the ball's speed.

Now, I drew my little diagram, solved for the force of tension (got 5.66N). I plug that in for my Centripetal Force in

Centripetal Force = mv^2/r, solve for v, and got 4.1 . The book gets like, 2.1. I'm getting so frustrated right now...let me know if you can help. Thanks.

 

[HallsofIvy]

Did you forget to take the SQUARE ROOT?

 

[M98Ranger]

I can understand your frustration, circular motion can be tricky to understand at times. However, it's important to stay calm and keep trying. Let's take a closer look at this problem and see where the discrepancy might be coming from.

First, let's make sure we are using the correct formula for centripetal force. The formula you have written, F = mv^2/r, is actually the formula for centripetal acceleration. The formula for centripetal force is F = mv^2/r. This may be the reason for the difference in your answer.

Next, let's check our calculations. When solving for the force of tension, did you take into account the horizontal and vertical components of the force? Remember, the force of tension is not acting directly in the horizontal direction, so we need to use trigonometry to find the horizontal component.

Lastly, let's check our units. The given mass is in kilograms, but the formula for centripetal force requires the mass to be in kilograms. Make sure all of your units are consistent throughout your calculations.

I hope this helps you understand where the discrepancy in your answer may be coming from. Remember, practice makes perfect and don't get discouraged. Keep trying and you will eventually get the hang of circular motion. Good luck!