Work Done Question

[Morokana]

A 95.0-kg crate is being pulled across a horizontal floor by a force P that makes an angle of 34.3° above the horizontal. The coefficient of kinetic friction is 0.284. What should be the magnitude of P, so that the net work done by it and the kinetic frictional force is zero?

i could not do this question .. i tried so much ! ... i tried finding out P.E. .. but wut do i do with the coefficient of kinetic friction ??... Work done = force X distance .. but wheres the distance .. please help me in this

 

[mezarashi]

Man, we should have a compilation of Physics Forums Solved Problems in Physics :P We could even sell it one day.

Alright so basically this is a force resolving problem. You need to resolve all the forces into their respective x and y components, Then do a summation of the forces. The question has stated that there is no acceleration in the x direction (forces are equal, Fnet = ma, Fnet = 0, a = 0). Obviously there is no acceleration in the y direction as well (it's on the floor).

Fnetx = 0
Fnety = 0

The trick is resolving the forces into the x and y components. But it seems like all the angles are given. I say give it a try.

 

[Morokana]

Thanx a lot man .. i got the answer right :) .. you do .. Fnet=95 x 9.8

then u multiply the answer by 0.284

 

[mezarashi]

Yup, then Pcos34.3 = Ffrict (in x).
So you didn't really need help after all ;)