Revolutions per sec (centripital acceleration)

[~christina~]

[SOLVED] Revolutions per sec (centripetal acceleration)

Homework Statement

As their booster rockets separate, space shuttle astronauts typically feel acclerations up to 3g where g= 9.80ms^2. In their training astronauts ride in a device in which they experience such accelrations as centripetal acceleration. Specifically, the astronaut is fastened securely at the end of a mechanical arm and that turns at constant speed in a horizontal circle.

determine the rotation rate in revolutions per sec required to give a astronaut a centripetal accelration of 3.00kg while in a circular motion with the radius of 9.45m

Homework Equations

$$a_c = v^2/r$$

T= 2pi*r/ v

The Attempt at a Solution

all I know is that the

$$a_c$$ = 3.00kg
and that

r= 9.45m

I'm not sure what I do with this though since wouldn't the accelration usually be in m/s^2 but in this case it is in kg...how can this be?

well I also don't have the velocity either...

I was thinking of substituting the centripetal accelration equation into the period T equation to get rid of v however I do know that speed is constant but velocity magnitude doesn't change since speed doesn't change but the magnitude I know does..

Can someone help me out with this...

Thanks

 

[Kurdt]

I think the question is supposed to say "centripetal acceleration of 3g" not 3.00 kg. Just seems like a typo. Your initial thoughts are quite correct. You can eliminate v to work out what T will be.

 

[~christina~]

thanks Kurdt

 

[Kurdt]

I don't think so. You will never get an acceleration reported in units of mass unless there is a typo or mistake.

 

[~christina~]

wait so how can it be in g then ??

you did say that it was in g not kg but now you say it can't be in units of mass...I'm confused..

 

[Kurdt]

g in this context is the acceleration due to gravity. So when somebody says there was an acceleration of 3g, they mean that the acceleration is 3 times the magnitude of the acceleration due to gravity. g was given in your question as g=9.80ms^-2.

 

[~christina~]

Oh I get it now... I thought it meant grams..
Thanks Kurdt