Help with Physics 11 Kinematics.

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Homework Help Overview

The problem involves a concrete block accelerating down a slope, specifically focusing on determining the coefficient of friction. The subject area is kinematics, with elements of forces and friction being discussed.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • The original poster attempts to apply equations related to forces acting on the block, including gravitational force components. Some participants question the use of an incorrect angle in calculations and suggest verifying the free body diagram.

Discussion Status

Participants are actively engaging in clarifying the setup of the problem, with some guidance offered regarding the importance of using the correct angle and considering the acceleration in calculations. Multiple interpretations of the forces involved are being explored.

Contextual Notes

There is a noted discrepancy in the angle used for calculations, with the original poster using 30° instead of the stated 34°. The discussion also highlights the need for clear unit usage in the problem-solving process.

aznpiggy
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Homework Statement



A 5.0kg concrete block accelerates down a 34° slope at 4.2m/s^2. Find the coefficient of friction between the block and the slope.


Homework Equations



Fg=5*9.8=45

x=45sin30

y=45cos30


The Attempt at a Solution



a=(mgsinθ-Ff)/m → Ff=mgsinθ-ma

Thanks
 
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Welcome to PF,
Have you drawn your free body diagram? How did you get your x and y components? The question states that the slope is at a 34° angle to the horizontal, not 30°.

Hint: Friction force = μN

Hint 2: Remember to add units to EVERYTHING.
 
Yes, I have drawn a FBD with x and y components that is perpendicular to the ramp.

I used the Fg to find the x by going Fgsin30°. Which would be the same as Fn.

Where would I go from this step?
 
aznpiggy said:
I used the Fg to find the x by going Fgsin30°. Which would be the same as Fn.

Why are you using 30° as your angle when it states in the question that it is 34°?

Your x component isn't the same as your y component, which would be the normal force (Fn). You must also consider the acceleration of the concrete block in your calculations.
 

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