# physics

a 330 kg piano slides 3.6 m down a 28 degree incline and is kept from accelerating by a man who is pushing back on it parallel to the incline. the effective coefficient of kinetic froction is 0.4. calculate

a) the force exerted by the man,
b)the work done by the man on the piano
c)the work done by the friction force
d) the work done by the force of gravity, and
e) the net work done on the piano.

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1. a.) the force exerted by the man is found by doing:
Fnormal= mass(gravity)(sin30) - u(mass)(gravity)(cos30)

...the u is the coefficient of friction.

b.) the work done by the man is found by using the force we found in the question above and putting it into:

W=Fd
My coeffiecent of friction was 0.40 so my total force was 421.5N

I just put it into W=421.5N(whateverdistanceIgiven)
for example is it was 9cm: (9cm = 0.09m)

W=421.5(0.09m) = 37.935J

c.) the work done by the friction force is solved the exact same way:
Since my coefficient of friction = 0.40 my Force of Friction = 0.41(280kg)(9.8m/s2)(cos30) = 950.5N

Then:
W=Fd = 950.5N(0.09m) = 85.545J

d.)the work done by gravity:
first find force of gravity by: mass(gravity)(sin30) = 1372N

then just plug into W=Fd = 1372(0.09m) = 123.48J

e.) the net work done on the piano = zero

I'm not sure if you noticed but the work of gravity minus the work of friction also gives you the work of the man!!

See: 123.48J - 85.545J = 37.935J !

Not sure if this was what your question was but... I remember doing this exact problem so I'm really hoping I was able to help you!!

-mayn zalik (not my real name :P...just a name I like)

Oh, and I'm sorry that I used different numbers. I copied and pasted my solution from my documents on my computer and these were my numbers. Just plug in your own numbers and get the answers :)

Once again, I'm really sorry BUT all the work is there!!

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2. my numbers were:

280Kg
30degrees
0.40
and then gravity which is always the same on earth :)

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3. my numbers were:

280Kg
30degrees
0.40
and then gravity which is always the same on earth :)

oh and 9cm which is 0.09m

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4. Thank you so much *zayn malik*

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