Question

two boys push on a box with 3 n and 6 n to the right. the net force is 7 n. find the force of friction.

Explanation:

Step1: Calculate the total pushing force

The two boys push to the right with forces \(F_1 = 3\space N\) and \(F_2=6\space N\). The total pushing force \(F_{push}=F_1 + F_2\).
\(F_{push}=3 + 6=9\space N\) (to the right)

Step2: Use the net - force formula

The net force formula is \(F_{net}=F_{push}-F_{friction}\) (since friction acts opposite to the direction of motion). We know \(F_{net} = 7\space N\) (to the right) and \(F_{push}=9\space N\) (to the right). Rearranging the formula for \(F_{friction}\), we get \(F_{friction}=F_{push}-F_{net}\)
Substitute the values: \(F_{friction}=9 - 7\)

Answer:

\(2\space N\) (opposite to the direction of the boys' push, i.e., to the left)