Awooden box weighing 150 n is sliding at a constant rate over a concrete sidewalk. the force required to pull the box at a steady rate is 78 n. what is the coefficient of friction?
1.9
228
72
0.52

0.52

Explanation:

The box is moving at constant velocity along the horizontal direction: this means that its acceleration is zero. According to Newton's second law:

where is the net force acting on the object, m its mass, and a its acceleration, since the acceleration is zero, then the net force must be zero as well.

There are in total 4 forces acting on the box:

- along the vertical direction: the weight of the box (downward), given by , and the normal reaction of the floor on the box (upward),

- along the horizontal direction: the force that pulls the box, , and the frictional force, which is given by , in the opposite direction

Since the net force is zero, the resultant on each direction must be zero. In the vertical direction we have:

While in the horizontal direction we have

So, the coefficient of friction is 0.52.

a.metals can become magnetic if they have many spinning electrons that create magnetic fields.d.only some metals are attracted by magnets; these metals are called ferromagnetic.

d.wrapping an insulated wire around a metal with ferromagnetic properties and applying an electric current.