Question

Three people are pushing a 500 kg of box in the same direction. applied forces are 30 n, 20 n, and 10 n respectively. if the acceleration of the box is 0.02 m/s2, what is the magnitude of a force created by friction?

Answer 1

The total force applied by the three people is:

`F=30 N+20 N+10 N=60 N`
This force is pushing toward the direction of the motion, while the frictional force
`F_f` points in the opposite direction.
We can write Newton's second law applied to the block: the resultant of the two forces must be equal to the product between the block's mass and its acceleration

`F-F_f = ma`
We know the mass of the block, m=500 kg, and the acceleration,
`a=0.02 m/s^2`, so we can find the friction:

`F_f = F-ma=60 N - (500 kg)(0.02 m/s^2)=50 N`