Question

A slowing force that occurs when one surface comes into contact with another is called ___

Answer 1

Answer:

Frictional force

Explanation:

Frictional force is a force that acts when there is a contact between two different surfaces, and it is due to the collisions between the molecules on the outermost layers of the two surfaces. The direction of the force is parallel to the two surfaces.

There are two types of frictional forces:

- Static frictional force: this force occurs, for instance, when you try to push an object over a surface, but the object does not move yet. In this case, the frictional force is acting against the direction of your push, preventing the object from moving. Assuming the surface is horizontal, its magnitude is given by

$F_s = \mu_s mg$

where

$\mu_s$ is the coefficient of static friction, which depends on the materials of the object and the surface

m is the mass of the object

g is the acceleration due to gravity

- Kinetic frictional force: this force occurs when you are pushing the object and the object is moving (sliding) along the surface. Again, the frictional force points against the direction of the motion, but this time the object is moving.  Assuming the surface is horizontal, its magnitude is given by

$F_k = \mu_k mg$

where

$\mu_k$ is the coefficient of kinetic friction, which depends on the materials of the object and the surface

Generally, $\mu_s > \mu_k$, so the static friction is always stronger than the kinetic friction (that's why it is more difficult to put an object in motion rather than keep it in motion)