# Circlar Motion

Discussion in 'Community Discussion' started by Quboid, Oct 14, 2007.

1. ### Quboid macrumors 6502

Joined:
Oct 16, 2006
Location:
everywhere
#1
Hello all,

Need some help on soem physics home work that has been keeping me up.
I can't find this one anywhere on he intnernet. here it is:

1. Can the angular velocity of an object be 0 while the angular acceleration is a non-zero? If yes what is the lineal equivalent to this situation. Give examples.

hopefully someone can figure this one out (I couldn't).

2. ### Leareth macrumors 68000

Joined:
Nov 11, 2004
Location:
Vancouver
#2
NO since acceleration is a measure of change in velocity over time.
Since you have zero change then zero accelaration
I may be wrong though. it has been 4 years since I touched Physics

Please learn to use spell check. that was painful to read through.

3. ### Schnebar macrumors 6502

Joined:
May 15, 2006
Location:
California
#3
I think it can happen

the angular velocity is just if it is spinning

it could be not spinning and just accelerating

Like a ball dropping to the ground that doesn't spin.

Does that work?

edit: ohh didn't read that we were talking about angular acceleration also.

Hmm back to thinking

4. ### mduser63 macrumors 68040

Joined:
Nov 9, 2004
Location:
Salt Lake City, UT
#4
I wrote out an answer then realized that it really isn't that hard of a question since it really only requires thinking (no particular knowledge of equations, etc) and you should be able to figure it out on your own. Hint: Think of a ball thrown straight up in the air.

5. ### Quboid thread starter macrumors 6502

Joined:
Oct 16, 2006
Location:
everywhere
#5
A ball thrown straight up in the air according to my understanding of physics pertains to free fall, and not circular motion. I wrote several answers to that question, I am just double checking with the peeps on MR. Thanks.

6. ### kainjow Moderator emeritus

Joined:
Jun 15, 2000
#6
I wish I could go back to studying motion. I am kept awake by trying to understand magnetic induction

7. ### Quboid thread starter macrumors 6502

Joined:
Oct 16, 2006
Location:
everywhere
#7

So you've already did motion. can you give that question a shot?

8. ### John Jacob macrumors 6502a

Joined:
Feb 11, 2003
Location:
Columbia, MD
#8
Free fall is only at a certain point after it starts coming back down. When it is thrown up, what happens? Think acceleration in the direction opposite the motion. And what happens when it reaches the top most point, just before it starts coming back down?

9. ### Oblivious macrumors 6502

Joined:
Jan 19, 2006
Location:
MA
#9
Nope. The angular acceleration of an object is equal to r x w(squared), where r is the radius and w (omega) is the angular velocity (angular velocity is also equal to v/r). So if omega is zero, then the angular acceleration is also zero.

Hope this helps.

10. ### Quboid thread starter macrumors 6502

Joined:
Oct 16, 2006
Location:
everywhere
#10

I have a pendulum that says yes. If the pendulum is at rest (in the middle of a period), it's angular velocity (omega) is zero, how ever it still have an angle and so has a direction change a so has acceleration. It also has gravity acting on it at that point.

http://en.wikipedia.org/wiki/Pendulum

11. ### crackpip macrumors regular

Joined:
Jul 23, 2002
#11
That is the centripetal acceleration i.e. proportional to the force required to keep the particle in circular motion. The angular acceleration is defined as the change in angular velocity (v/r) divided by the interval of time. Restating the question you first posted: is it possible for the angular velocity to be changing even if, at a specific instance in time, the angular velocity is zero?

crackpip