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strugglin-physics
Oct3-04, 04:59 PM
A wet bar of soap slides freely down a ramp 9.35 m long inclined at 7.00°. How long does it take to reach the bottom? Assume muk = 0.0550.

Okay I've got my x & y componants
9.35cos(7)=9.28
9.35sin(7)=1.14

But now what since I don't have the mass of the soap or the acceleration, what do I do next?

e(ho0n3
Oct3-04, 05:06 PM
Draw yourself a free-body diagram of the situation. It should be pretty clear to you from then on.

strugglin-physics
Oct3-04, 05:35 PM
Okay I drew my FBD but I still don't know how much time it would take the soap to slide down the ramp. Maybe I'm missing something.
I have the frictional force going NW the normal force going NE and the weight force going South... is that right?

e(ho0n3
Oct3-04, 05:37 PM
Yes. Set up the equations using Newton's 2. law, solve for the acceleration and use some kinematics to solve for time.

strugglin-physics
Oct3-04, 06:27 PM
How do I solve for acceleration if the mass is unknown?

arildno
Oct3-04, 06:33 PM
Well, but since the frictional force, the gravity and the "ma" terms are all proportional to the mass, it's a common factor which you can eliminate
(the solution is independent of the mass)