Lab - Friction and Forces on an Incline

AI Thread Summary
To calculate the coefficient of sliding friction (μk), the average force of sliding friction (0.32N) should be divided by the normal force (Fn), which is derived from the weight and angle of the incline. The correct formula is μk = Ff/Fn, where Ff is the force of friction. The normal force can be expressed as Fn = mg cos(θ), where θ is the angle of the incline. The discussion clarifies that the average force of friction should not be treated as an angle, and the relationship between the forces acting on the object must be considered. Understanding these relationships is crucial for accurately determining the coefficient of sliding friction.
soccergirl14
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Okay, so I am writing a lab but I am quite stuck on one question.

Using the average force of sliding friction from the data, calculate the coefficient of sliding friction.
Average force of sliding friction: 0.32N

The equation I used to calculate other static/sliding coefficients was:
(FgSinX)/(FgCosX)
And X is the value of an angle.

I am confused because I don't know if I can use this formula to calculate the coefficient because the average force of sliding friction is not an angle.

If I use the average force of sliding friction as an angle I get:
(9.8xSin0.32)/(9.8xcos0.32) = 0.006
This does not seem right, anyone have any ideas?
please and thanks.
 
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soccergirl14 said:
Okay, so I am writing a lab but I am quite stuck on one question.

Using the average force of sliding friction from the data, calculate the coefficient of sliding friction.
Average force of sliding friction: 0.32N

The equation I used to calculate other static/sliding coefficients was:
(FgSinX)/(FgCosX)
And X is the value of an angle.

I am confused because I don't know if I can use this formula to calculate the coefficient because the average force of sliding friction is not an angle.

If I use the average force of sliding friction as an angle I get:
(9.8xSin0.32)/(9.8xcos0.32) = 0.006
This does not seem right, anyone have any ideas?
please and thanks.

Don't you want to look to the definition of μk?

μk = Ff/Fn

If you have determined Ff, then aren't you just interested in dividing by the Fn ?
 
Okay, thank you, I think I understand.
What I tried was:
(0.32N)/(9.8cosX)
Would that make sense?
 
soccergirl14 said:
Okay, thank you, I think I understand.
What I tried was:
(0.32N)/(9.8cosX)
Would that make sense?

Not quite.

The normal force is given by cosθ * weight, but there is also the component of gravity down the incline of sinθ * weight. If the force you are measuring pushing up the ramp is .32N then isn't that the result of the relationship that

.32 N = μ*m*g*cosθ + m*g*sinθ

If .32N is measured pushing down the ramp then

.32N = μ*m*g*cosθ - m*g*sinθ
 
Okay I get it!
thank you so much for the help!
 

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