Calculating Force Needed to Stop Piano on 27° Incline

[Bones]

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!

 

[PhanthomJay]

Bones, welcome to PF!

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!

 

[Bones]

I must be dyslexic because I worked on that problem for hours and didn't notice that once! Thanks ;)