Calculating Time it Takes for Soap to Slide Down a Ramp

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Homework Help Overview

The discussion revolves around calculating the time it takes for a wet bar of soap to slide down a ramp that is 9.35 m long and inclined at 7.00°. The problem involves concepts from dynamics and kinematics, particularly focusing on forces acting on the soap and the effects of friction.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss breaking down the problem into components and drawing free-body diagrams. Questions arise about how to determine acceleration without knowing the mass of the soap, and there is exploration of the relationship between forces and mass in the context of Newton's second law.

Discussion Status

Participants are actively engaging with the problem, offering guidance on using free-body diagrams and Newton's laws. There is a recognition that the mass can be eliminated from the equations, suggesting a productive direction in the discussion.

Contextual Notes

There is an assumption that the frictional coefficient is known, but the mass of the soap is not provided, which raises questions about how to proceed with the calculations.

strugglin-physics
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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?
 
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Draw yourself a free-body diagram of the situation. It should be pretty clear to you from then on.
 
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?
 
Yes. Set up the equations using Newton's 2. law, solve for the acceleration and use some kinematics to solve for time.
 
How do I solve for acceleration if the mass is unknown?
 
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)
 

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