Assuming that Albert's push and the friction with the floor are the only horizontal forces acting, what is the magnitude of the frictional force pushing backward on the box

F_f = 25 N

Explanation:

Given:

- Force applied by Albert F = 49 N

- Mass of the box m = 12 kg

- Acceleration of the box a = 2 m / s^2

- Frictional Force = F_f

Find:

what is the magnitude of the frictional force pushing backward on the box

Solution:

- Apply newton's second Law of motion on the box. With the applied force and the frictional are the only horizontal forces. Applied force in the direction of acceleration and Frictional Force F_f opposite in direction of the motion. Then we have from the Equation of motion:

F_net = m*a

F_net = F - F_f

F - F_f = m*a

- Plug in the values:

F_f = F - m*a

F_f = 49 - 12*2

F_f = 25 N