someone help me understand this

Question

el_arrow · Answer

attachment

el_arrow · Answer

why is the kintetic friction (fk) negative if its going to the right?

el_arrow · Answer

shouldn't the mgsin(theta) be negative instead because its going to the left?

el_arrow · Answer

@abhisar @Pompeii00

anonymous · Answer

@lanK16 @TreyYoung

anonymous · Answer

@TreyYoung can you privte message me??

el_arrow · Answer

dude can you answer my question

anonymous · Answer

please??!!

irishboy123 · Answer

it's just a common sense sign convention, divorced from the usual x-y-z cartesian convention.

so, the component of gravity along the surface of the wedge (mgsinø) goes to the left.  AND friction opposes the motion this force wishes to induce, and thus acts to the right.  

BUT this follows from the fact that motion to the left is positive as the net force, should motion occur, is in that direction.  all of which follows from he way the wedge was drawn in the first place!!  IE it could have pointed in the other direction.

to make the point clear, you could just as easily model gravity as an upward force with a negative value.  ie signifying that it acts downwards.  you could have included horizontal gravity, with a magnitude of zero.  it's all just relative.