HELP please!

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HELP please!

Postby Jared » Tue Sep 23, 2003 5:35 pm

Hi all! I need help! If there are any Physics people out there would you give me a hand?

Block A of weight W slides down an inclined plane S of slope angle 37 degrees at constant velocity while plank B, also of weight W, rests on top of A.  The plank is attached by a cord to the top of the plane.

If the coeffecient of kinetic friction is the same between the surfaces A and B and between S and A determine its value.

can anyone make sense of this?

Thanks in advance,

Jared
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Re: HELP please!

Postby Smoke2much » Wed Sep 24, 2003 1:42 am

Nope sorry, physics failure here.  My trick with physics was to not try and understand it but simply accept that it was so.  I failed.....

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Re: HELP please!

Postby JW » Wed Sep 24, 2003 6:29 am

Since the speed of A (+B) (total weight 2W) down slope S is constant, the kinetic energy is constant. Normally the kinetic energy would rise, due to the decline of potential energy.
Here, potential energy is declining, kinetic ISN'T rising, because of the 2 friction coef's (since there are 2 friction planes) between A-B and A-S

Through the slope angle you should be able to determine the amount of energy (normally turned into kineticE) that is lost on the 2x friction coeff.

Meaning: why isn't block A accelerating? because the friction of B onto A and A+B onto S keeps it constant.

Long way back, man, I may be wrong here, anyone else make sense of this?
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Re: HELP please!

Postby Jared » Wed Sep 24, 2003 7:39 am

Hey! Thanks for the info, some of is seems to make sense, sounds like I was on the right track, but I wasn't sure.  

Thanks for all of the info!

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