A box weighs 1300 N. When a horizontal force of 390 N has applied the box accelerates at 1.3 m/s2. What is the magnitude of the frictional force?

Ffriction = 217.7[N]

Explanation:

First, we must find the mass of the box, we must remember that the weight is defined as the product of the mass by acceleration.

where:

w = weight [N] (units of Newtons)

m = mass [kg]

g = gravity acceleration = 9.81 [m/s²]

Now we must use Newton's second law, which tells us that the sum of forces is equal to the product of mass by acceleration.

∑F = m*a

where:

∑F sum of forces

m = mass = 132.51[kg]

a = acceleration = 1.3[m/s²]

We must know that the forces that act are the horizontal force that moves the box and the friction force in the negative direction that acts against the movement.

Now replacing:

the right answer is 0.3 meters per second