Friction and Gravity

What is friction?

The force that two surfaces exert on each other when they rub against each other.

What factors determine the strength of friction?

1. How hard the surfaces push together 2. The types of surfaces involved (smooth, rough)

What is static friction?

Friction that acts on objects that are not moving.

How can static friction be helpful?

Examples include spreading sand or salt on icy sidewalks and bike brakes where rubber pads slide against the tire.

What is sliding friction?

Friction that occurs when an object rolls across a surface, commonly used in roller skates, bikes, and skateboards.

What is rolling friction?

Friction that occurs when a solid object moves through a fluid, such as water skiing, wakeboarding, swimming, or riding a bike.

What is fluid friction?

A force that opposes the motion of an object moving through a fluid.

What is gravity?

A force that pulls objects toward each other.

What factors affect gravity?

1. Mass 2. Distance

How does mass affect gravitational force?

The more mass an object has, the greater its gravitational force.

How does distance affect gravitational force?

The farther two objects are from one another, the lesser the gravitational force between them.

What is free fall?

When the only force acting on an object is gravity.

What is projectile motion?

The motion of an object thrown horizontally.