# Friction and motion relationship

### Friction - Concept, How it works, Real-life applications, Key terms

What is friction? Friction is the resistance of motion when one object rubs against another. Anytime two objects rub against each other, they cause friction. Once in motion it is easier to keep it in motion than it was to get it started, indicating that the kinetic frictional force is less than the maximum static frictional force. Friction is the force that resists motion when the surface of one object comes into contact with the surface of another. In a machine, friction reduces the.

The fact is that force is so fundamental that it defies full explanation, except in terms of the elements that compose it, and compared to force, friction is relatively easy to identify. In fact, friction plays a part in the total force that must be opposed in order for movement to take place in many situations.

• What is the relationship between friction and motion?
• What is friction?
• Friction Basics

So, too, does gravity—and gravity, unlike force itself, is much easier to explain. Since gravity plays a role in friction, it is worthwhile to review its essentials. Newton's first law of motion identifies inertia, a tendency of objects in the physical universe that is sometimes mistaken for friction.

When an object is in motion or at rest, the first law states, it will remain in that state at a constant velocity which is zero for an object at rest unless or until an outside force acts on it. This tendency to remain in a given state of motion is inertia.

Inertia is not a force: Inertia is, however, a component of force, since mass is a measure of inertia. In the case of gravitational force, mass is multiplied by the acceleration due to gravity, which is equal to 32 ft 9. People in everyday life are familiar with another term for gravitational force: Weight, in turn, is an all-important factor in friction, as revealed in the three laws governing the friction between an object at rest and the surface on which it sits.

According to the first of these, friction is proportional to the weight of the object. That's why there are often so many accidents.

Even though the friction of the brakes is still there, the brakes may be wet, and the wheels are not in as much contact with the ground. Cars hydroplane when they go too fast on puddles of water.

### Physics for Kids: Friction

Friction and Gases Friction only happens with solid objects, but you do get resistance to motion in both liquids and gases. This doesn't involve sliding surfaces like friction does, but is instead the kind of resistance you get if you try to push your way through a crowd.

It's a colliding situation, not a sliding one. If the gas is air, this is referred to as air resistance. If you were in the space shuttle and re-entering the atmosphere, the bottom of the shuttle would be getting very hot.

The collisions that occur between the molecules of the air being compressed by the shuttle, heat up the air AND the shuttle itself. The temperature on the top of the shuttle is also warm, but nowhere near the temperatures found on the bottom. Friction and Liquids Although liquids offer resistance to objects moving through them, they also smooth surfaces and reduce friction.

Liquids tend to get thinner less viscous as they are heated. However, the energy doesn't disappear. It changes from moving energy also call kinetic energy to heat energy. This is why we rub our hands together when it's cold. By rubbing them together we generate friction and, therefore, heat.

## Air resistance and friction

The force F of friction pushes back on the block. Preventing Friction In some cases we want to prevent friction so it's easier to move. A good example of this is a ball or wheel.

They roll to help reduce friction.

Another way to reduce friction is with a lubricant like grease or oil. Machines and engines use grease and oil to reduce friction and wear so they can last longer. Another way to reduce friction is to change the types of materials in contact with one another. For example, ice contacting with steel would produce less friction than rubber would on concrete. This is why ice skates slide so easily on the ice, but you don't slip when wearing rubber shoes on the sidewalk.

These different materials are said to have different "coefficients of friction".