Question #e7c74

1 Answer
Aug 19, 2017

"net force" = 0

"friction force" = 100 "N" (directed opposite to applied force)

Explanation:

We're asked to find

  • the net force acting on the crate

  • the magnitude of the friction force acting on the crate

" "

  • Net force

We're given that 100 "N" of applied horizontal force is necessary so that the crate moves at a constant speed across the floor.

Since it is moving at a constant speed, it has zero acceleration, and according to Newton's second law, the net force is zero:

F_"net" = ma

color(red)(ulbar(|stackrel(" ")(" "F_"net" = m(0) = ul(0)" ")|)

" "

  • Friction force

Since we know the net force is zero, then the vector sum of the applied force and the friction force is equal to 0:

F_"net" = F_"applied" - F_"friction" = 0

We're given that the applied force is 100 "N", so we have

100color(white)(l)"N" - F_"friction" = 0

And so

color(blue)(ulbar(|stackrel( "")(" "F_"friction" = 100color(white)(l)"N"" ")|)

in the opposite direction of the applied force.