# Velocity of an object Rotating in vacuum , Gravity applies

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1. Feb 23, 2015

### SeeKeeDeeDoo

I was wondering what might happen If we for instant, Rotated a ball around an axis in a vacuum chamber.
First, If the initial speed was 20m/s would it remain like that forever, hypotheticaly saying No friction exists and that Air Resistance does not exist as the Ball rotates in vacuum.

Also Will centripital force cancel out gravity if the speed is high enough to produce 9.81m/s2 Acceleration?

Also Will Tension Affect Speed ?

2. Feb 23, 2015

### SteamKing

Staff Emeritus
An object in a vacuum chamber on earth is still affected by gravity. Unless you levitated the ball in the vacuum chamber so that its surface did not touch anything, eventually friction would retard the spin of the ball.

A spinning ball is still affected by gravity, whether or not it's in a vacuum chamber. Remember, gravity attracts an object toward the center of the earth.

It's not clear what tension you are talking about.

3. Feb 23, 2015

### SeeKeeDeeDoo

I haven't totally understood your answer.
To be more simple, would the ball "Which is tied to a rope and the other end of the rope is tied to a pole" projected at 20 m/s Maintain its speed in vacuum **assuming No friction exists, Only gravity exists**

The tension in the rope.

4. Feb 23, 2015

### SteamKing

Staff Emeritus
If the ball is tied to anything, the friction in the rope or the friction between the rope and what it's tied to is eventually going to bring the motion of the ball to a stop. The presence of a vacuum is not, by itself, going to eliminate friction between objects in contact with one another.

5. Feb 23, 2015

### nasu

If you assume that friction does not exist anyway, what is the point of the vacuum?
What do you think will the vacuum change in the problem, as compared with the situation in air?

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