Calculation Error?

polarized

Hello,

I'm in the middle of a problem on the online program Webassign, trying to calculate the coefficient of friction in a problem. I have the correct value of the force of friction, and I believe I have the correct Normal Force value, but the program is rejecting my answer.

The problem involved a 21kg box sliding down a 38 degree inclined plane at an acceleration .270 m/s^2, and I calculated the force of friction to be 121.033N. To solve for the coefficient of friction I am using the equation Ff=uFn → u=Ff/Fn= 121.033N/205.8N=.588

Did I make an error or is it a glitch in the program?

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arildno

Homework Helper
Gold Member
Dearly Missed
Your normal force is incorrect, it seems.
If you used N=mg, that's where your mistake lies.

polarized

ooh yikes, thank you, I didn't notice that. And I drew the vector diagram too, so I should've realized lol. Thank you!

ColdRifle

Use g as 9.81m/s^2 and not 9.8m/s^2 and you might get the right answer

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