Calculating Work Done on a Slope: Friction and KE

[disruptors]

Hey ppl,

If you have a man pushing a box up a slope with a horizontal force at constant speed from distance a to b, can one assume the Work done by friction to be zero all the time since velocity is constant? or can one assume W(neoconservative)=change in U(gravitational PE) only, with change in KE=0...

Thanks

 

[Sirus]

can one assume W(neoconservative)=change in U(gravitational PE) only, with change in KE=0...

Yes, but only if the man is a neoconservative.

 

[quasar987]

hahaha

Hey ppl,

If you have a man pushing a box up a slope with a horizontal force at constant speed from distance a to b, can one assume the Work done by friction to be zero all the time since velocity is constant?

Well that would be true if the frictionnal force depended on the accelaration of the thing sliding on the surface. But it's usually not the case, and we can assume that the frictionnal force depends only on the weight of the box and on the coeficient of friction of the surface, such that f = Nµ = mgµ. So the work done by the fricton would have to be component of friction parallel to the surface times the distance b-a.