Forces

FORCES

A force is a push or a pull on an object; when one object pushes or pulls another we say that it exerts a force. There are several different types of forces, but they can all be described in terms of their strength and direction.

Types of Forces

Gravity is an attractive force between any two objects with mass. Its strength depends on the amount of mass the objects have and the distance between them. Because the mass of the Earth is so much larger than any other object we encounter on a daily basis, we tend to think of gravity as the force that attracts us to Earth. However, all objects with mass exert a gravitational force on objects near them. Because gravity acts on objects at a distance (without touching them), we classify it as a non-contact force.

Hammer vs. Feather on the Moon

Magnetism is another example of a non-contact force.

When one object applies a force to another by touching it, we call it a contact force. Throwing a ball or pushing a box would be examples of an applied contact force. Friction, also, would be considered a contact force because it only occurs when two surfaces rub against one another.

Mass vs. Weight

COMMON MISCONCEPTION: Weight and mass refer to the same thing.

REALITY: Mass is a physical property, referring to the amount of matter in an object. Weight is a force, measuring how strong the force of gravity pulls on a mass.

An object's weight is a measure of the force of gravity on that object's mass. Changing the gravitational attraction (for example, going to the Moon or another planet) will change an object's weight, but not its mass.