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Help with Physics 11 Kinematics.

  • Thread starter aznpiggy
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  • #1
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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
 

Answers and Replies

  • #2
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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.
 
  • #3
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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?
 
  • #4
92
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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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