Solving Physics Questions: Acceleration & Friction Coefficient

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Homework Help Overview

The discussion revolves around two physics problems involving acceleration on an inclined plane and the coefficient of friction between a coin and a book. The first problem asks for the acceleration of a cart rolling down a ramp inclined at 27 degrees, assuming frictionless wheels. The second problem involves determining the coefficient of friction when a coin remains stationary until the book is opened to a 25-degree angle.

Discussion Character

  • Mixed

Approaches and Questions Raised

  • Participants explore the use of Newton's second law (F=ma) for the first problem and discuss the forces acting on the cart. There are questions regarding the choice of forces, specifically why mg*sin(27) is used instead of mg*cos(27). For the second problem, participants discuss the relationship between the force of friction and the normal force, questioning how to derive the coefficient of friction without knowing the mass.

Discussion Status

The conversation is active, with participants providing different approaches to the problems. Some guidance has been offered regarding the application of forces, but there is still uncertainty and confusion about the underlying principles and calculations. Multiple interpretations of the problems are being explored.

Contextual Notes

Participants note the assumption of frictionless wheels in the first problem and the lack of mass information in the second problem, which complicates the calculations. There is an emphasis on understanding the forces involved rather than simply applying formulas.

staz13
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Hey guys! I REALLY need some help with my physics. Here is one of my two questions:

1) With what rate of acceleration will a cart roll down a ramp inclined at an angle of 27 degrees? Assume the wheels of the cart are frictionless

I have NO idea how to even get started.

Here is the second one, 2) A coin is placed on a book that is slowly opened. It is noted that the coin does not start to move until the opening angle is 25 degrees. What is the coeficient of friction between the book and the coin?

THANKYOU in advance if you can help at all!
 
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1.use F=ma for the first one. So mgxsinx27=ma, then gxsin27=a

2. Use f=un, so mgcos25=Normal.

Maybe use F-f=ma to find f then use f=un to find coefficient of friction
 
For question 1 I got 4.45 m/s ^2. But i don't understand why you used mgsin27. How do we know that's the force? and not mgcos27

For question 2 i don't understand how you went from force of friction = unormalforce to mgcos25 . I also don't see how it helps because we don't have the mass.
 
mgcos always equals the normal force. Unless its an object on the ground, which in that case w=n.

Alright. f=un. mgcosx25=n

f=uxmgcos25

mgxsin25=uxmgcos25

gxsin25=uxgcos25
g=9.8
solve for u
 

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