What Is the Correct Coefficient of Friction Calculation?

AI Thread Summary
The discussion centers on calculating the coefficient of friction for a block weighing 8.1 N, which requires a force of 2.8 N to move at constant velocity. The correct equation to find the coefficient of friction (Cf) is 2.8 N = Cf * 8.1 N, leading to a coefficient of approximately 0.34567. For the second part, when an additional weight W is added, a force of 4.8 N is needed to maintain constant velocity, allowing the equation 4.8 N = 0.34567 * (8.1 N + W) to be used to solve for W. The calculated weight W is approximately 5.7857 N, with a suggestion to round to appropriate significant figures.
anglum
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A block weighing 8.1 N requires a force of
2.8 N to push it along at constant velocity.
What is the coeficient of friction for the
surface?

002 (part 2 of 2) 10 points
A weight W is now placed on the block and
4.8 N is needed to push them both at constant
velocity.
What is the weight W of the block? Answer
in units of N.



For part 1 i used the equation 2.1N = Cf * 8.1N
and solved for Cf or coefficient of friction

that was incorrect tho
 
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anglum said:
For part 1 i used the equation 2.1N = Cf * 8.1N
and solved for Cf or coefficient of friction
Shouldn't that be 2.8 N? (Assuming the force is applied horizontally.)
 
yeah i mistyped that it should be

2.8N = Friction * 8.1N

Friction = .34567 ?

is that correct? if i have that then i can solve the 2nd one

by taking
4.8= .345679 *(8.1N+W) and solve for W?
 
and in solving for W there i get 5.7857 N
 
Looks good to me. (You may want to round off your answer to a reasonable number of significant figures--especially if you're using an online system.)
 

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