Swinging Ball at Top of Circle: Forces & Energies

[sarah adam]

1. A 0.160 kg ball attached to a light cord is swung in a vertical circle of radius 70.0 cm. At the top of the swing, the speed of the ball is 3.26 m/s. The centre of the circle is 1.50 m above the floor.

a. Draw a free-body diagram of the forces on the ball at the top of the swing.

b. Calculate the magnitude of the tension in the cord at the top of the swing.

c. With respect to the floor, calculate the mechanical energy of the ball at the top of the swing

d. Calculate the speed of the ball when the cord is 30.0̊ below the horizontal

e. Determine the magnitude of the tension in the cord when the cord is 30.0̊ below the horizontal

 

[Zack K]

You should probably maintain the format of the homework section or else moderators will remove it.

 

[sarah adam]

You should probably maintain the format of the homework section or else moderators will remove it.

thanks for the headsup man. I'm currently updating it.

 

[jedishrfu]

And we are awaiting your changes...

 

[sarah adam]

And we are awaiting your changes...

okay give me some time geez

 

[jedishrfu]

It's a bit of humor on my part...

Read my signature quote from Day the Earth Stood Still.

I'm a robot so what do you expect?

 

[jedishrfu]

Okay, so your free body diagram shows the rope tension going downward.

Is that right?

What happened to the homework template? You know the three questions that we ask?

 

[sarah adam]

Okay, so your free body diagram shows the rope tension going downward.

Is that right?

yes, it does.

 

[jedishrfu]

If I spin the weight in a vertical circle and let go, will the ball go up or drop down?

 

[sarah adam]

If I spin the weight in a vertical circle and let go, will the ball go up or drop down?

drop because of gravity

 

[jedishrfu]

Okay you're right about the tension.

 

[sarah adam]

Okay you're right about the tension.

not sure if my diagram is 100% right, along with my answers for b and c. Also, how do I go about d and e?

 

[jedishrfu]

I found this discussion at Hyper Physics:

http://hyperphysics.phy-astr.gsu.edu/hbase/Mechanics/cirvert.html

and this one at Study Physics:

http://www.studyphysics.ca/newnotes/20/unit02_circulargravitation/chp07_2d/lesson31.htm

It should get you started.

 

[sarah adam]

I found this discussion at Hyper Physics:

http://hyperphysics.phy-astr.gsu.edu/hbase/Mechanics/cirvert.html

It should get you started.

u a real 1

 

[sarah adam]

I found this discussion at Hyper Physics:

http://hyperphysics.phy-astr.gsu.edu/hbase/Mechanics/cirvert.html

and this one at Study Physics:

http://www.studyphysics.ca/newnotes/20/unit02_circulargravitation/chp07_2d/lesson31.htm

It should get you started.

I think I'm good for a) and b) because you sent me those links. although, I'm not sure on how to incorporate the angle in for d) and e)

 

[jedishrfu]

Show us some work on d and e. Its a bit beyond what I can help with but some homework helper will sign on soon.

We can't always promise that questions will be answered quickly here especially on the weekend. It all depends on when our advisors and homework helpers sign on.

Try using the references I gave you and see if you can work it out.

 

[Zack K]

I think I'm good for a) and b) because you sent me those links. although, I'm not sure on how to incorporate the angle in for d) and e)

For d, start with finding the energy at the top of the motion, then think of how you can use the idea of conservation of energy to solve it.