Question

Question #e7c74

Answer 1

`"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.