# The force of friction

Confusion of Mass and Weight A few further comments should be added about the single force that is a source of much confusion to many students of physics - the force of gravity. As mentioned abovethe force of gravity acting upon an object is sometimes referred to as the weight of the object.

Until now in physics, you've probably been ignoring friction to make things simpler. Now, it's time to include this very real force and see what happens.

What are the forces of static and kinetic friction? Parking your car on the steep hills of San Francisco is scary, and it would be impossible without the force of static friction. This is the same force that allows you to accelerate forward when you run. Your planted foot can grip the ground and push backward, which causes the ground to push forward on your foot.

## Vetconnexx.com: Do an experiment with friction

We call this "grippy" type of friction, where the surfaces are prevented from slipping across each other, a static frictional force. If there were absolutely no friction between your feet and the ground, you would be unable to propel yourself forward by running, and would simply end up jogging in place similar to trying to run on very slippery ice.

Now, if you park on a hill that is too steep, or if you are being pushed backward by a Sumo wrestler you're probably going to start sliding.

Even though the two surfaces are sliding past each other, there can still be a frictional force between the surfaces, but this sliding friction we call a kinetic frictional force.

For example, a person sliding into second base during a baseball game is using the force of kinetic friction to slow down.

## What Is Friction?

If there were no kinetic friction, the baseball player would just continue sliding yes, this would make stealing bases in baseball difficult.

But if you were to zoom in, you would see that the surfaces are rough at a microscopic level. For instance, the surfaces of the box and floor as shown below are actually rough and jagged at a microscopic level. Openstax College Physics Friction arises in part because of the roughness of the surfaces in contact, as seen in the expanded view.

In order for the object to move, it must rise to where the peaks can skip along the bottom surface. Thus a force is required just to set the object in motion. Some of the peaks will be broken off, also requiring a force to maintain motion.

• What Causes Friction?
• Inclined planes and friction

Much of the friction is actually due to attractive forces between molecules making up the two objects, so that even perfectly smooth surfaces are not friction-free. Such adhesive forces also depend on the substances the surfaces are made of, explaining, for example, why rubber-soled shoes slip less than those with leather soles.

## Types of Forces

But to be completely honest, we still don't have a complete understanding of the microscopic causes of friction. More recent research in tribology study of sliding surfaces suggests that vibration in the surfaces, leading to energy loss through heat, is a main source of friction.

For each of the following cases of a car changing velocity described in the table below, choose whether it is more likely to be the force of static or kinetic friction causing the change in velocity.Calculate the force of friction using the formula: F = μN Where N is the normal force and μ is the friction coefficient for your materials and whether they’re stationary or moving.

What is friction and what is a coefficient of friction. The resistance to lateral motion when one attempts to slide the surface of one object over another surface is called friction or vetconnexx.coming on the type of materials that are in contact, the force one needs to overcome friction can vary.

Force, in mechanics, any action that tends to maintain or alter the motion of a body or to distort it.

## Calculating the Force of Friction

The concept of force is commonly explained in terms of Isaac Newton’s three laws of motion set forth in his Principia Mathematica (). According to Newton’s first principle, a body that is at rest or moving at a uniform rate in a straight line will remain in that state until some force.

Nov 21,  · An interactive track on which children can explore the effect of friction with different track surfaces. A force is a push or pull acting upon an object as a result of its interaction with another object.

There are a variety of types of forces. Previously in this lesson, a variety of force types were placed into two broad category headings on the basis of whether the force resulted from the contact or non-contact of the two interacting objects.

Friction. Frictional resistance to the relative motion of two solid objects is usually proportional to the force which presses the surfaces together as well as the roughness of the vetconnexx.com it is the force perpendicular or "normal" to the surfaces which affects the frictional resistance, this force is typically called the "normal force" and designated .

Forces and Motion - Force | Position | Velocity - PhET Interactive Simulations