1. Chapter 12: Forces and Motion
Section 12.4
Universal Forces

2. Electromagnetic Forces
Associated with charged particles
Electric forces
Occur between charged objects like protons and electrons
Magnetic forces
Act on certain metals, poles of magnets, etc.
Only types of forces that can both attract and repel
Opposites attract
Like repels like

3. Nuclear Forces
Strong and weak nuclear forces hold the nucleus of an atom together.
Strong nuclear force (remember this?)
Holds neutrons and protons together
Only acts over short distances
Weak nuclear force
Attractive force that acts only over short distances
Weaker than the strong nuclear force

4. Gravitational Force
An attractive force that acts between any two masses
Weakest universal force
Most effective over large distances
Newton’s law of universal gravitation
Says that every object in the universe attracts every other object
The greater the mass of an object, the greater the gravitational force.
The more distance between two objects, the less the gravitational force.

5. Centripetal Force
A force that constantly changes the direction of an object and causes it to move in a circle
Examples affected by centripetal force:
Moon
Satellites
Examples (there are too many to list) of satellite uses include:
communication
tracking Earth’s weather and climate