Calculating Force Needed to Stop Piano on 27° Incline

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AI Thread Summary
To calculate the force exerted by a man to stop a 399 kg piano sliding down a 27° incline, the correct approach involves using the equation mg(sin27) - (mu)mg(cos27) = F_applied. The user initially calculated using an incorrect mass of 339 kg, leading to an erroneous result of 324N. Upon realizing the mistake in mass, the user acknowledged the need to recalculate using the correct mass. The effective coefficient of kinetic friction is 0.40, which is crucial for determining the frictional force. Accurate calculations are essential for solving physics problems involving forces on inclines.
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Homework Statement


A 399 kg piano slides 3.6 m down a(n) 27° incline and is kept from accelerating by a man who is pushing back on it parallel to the incline. The effective coefficient of kinetic friction is 0.40. Calculate the force exerted by the man.




Homework Equations





The Attempt at a Solution



Ok, I took mg(sin27)-(mu)mg(cos27)=0
339kg*9.8m/s^2*sin27-0.40*339kg*9.8m/s^2*cos27=0 and got 324N for an answer which is apparently not correct. I tried it several different ways and keep coming up with the same answer. Please help!
 
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Bones, welcome to PF!
Bones said:
Ok, I took mg(sin27)-(mu)mg(cos27)=0
you mean = F_applied by man, not 0.
339kg*9.8m/s^2*sin27-0.40*339kg*9.8m/s^2*cos27=0 and got 324N for an answer which is apparently not correct. I tried it several different ways and keep coming up with the same answer. Please help!
The problem statement notes the mass as 399 kg, but you used 339 kg!
 
I must be dyslexic because I worked on that problem for hours and didn't notice that once! Thanks ;)
 

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