3. A worker pushes a box across the floor to the right at a constant speed with a force of 25N. What
can you conclude about the box?

An unbalanced force of 25N is acting on the box
Friction between the box and the floor is 25N to the left.
The net horizontal force acting on the box is 50N.

Friction between the box and the floor is 25N to the left.

Explanation:

According to Newton's second law of motion, the net force acting on an object is equal to the produce between the object's mass and its acceleration:

where

m is the mass of the object

a is its acceleration

In this problem, we have two forces acting on the object:

- The applied force, F = 25 N, to the right

- The force of friction , opposing the motion of the box, so to the left

So we can write the net force as

Also, we know that the box is moving at constant speed: this means its acceleration is zero, so

Therefore

WHich means:

And therefore,

which means that the force of friction is also 25 N.

trig 15.3 cos