The Four Forces of Nature
A Brief Introduction
The forces of nature are responsible
for providing the energy we used
everyday!
Recall…Energy comes from matter
and energy and matter are reversible.
The forces of nature from weakest to
strongest:
Gravity > Weak Force > Electromagnetic Force > Strong Nuclear
Weakest
>>>>>>>>>>>>>>>>>>>>>>>>>>
Strongest
The Gravitation Force (Weakest)
• Attractive force between ALL MASS in the
universe
• Unusual in that it is ALWAYS attractive
• The weakest of all forces
• Has infinite range (acts across the entire
universe)
• The “particle” that carries the force is called a
graviton but is has never been found!!
The Weak Force
• Acts at extremely small distances within the nucleus.
• Responsible for radioactive decay of elements called betadecay.
• Occurs when a neutron is changes into a proton or a proton
changes into a neutron (very strange). This changes the
identity of the element!!
• Energy is released in the form of electrons and can do work.
The Electromagnetic Force
• Most familiar to us.
• Is the attractive force between positive and negative
charges and the repulsive force between like charges
particles.
• Holds you together, the atoms of your chair,
everything around you!!
• Electricity, magnetism and light are all examples of
this force.
• Has infinite range
• The photon is the “messenger” particle of this force.
What is making the iron fillings move away and towards the
magnet spontaneously? Answer: photons are being exchanged
between the magnet and the iron fillings..you just can’t see
them!
http://www.youtube.com/watch?v=Dn6VVZ3mrs4&feature=related
Is light magnetic? YES!! Another term for light is electromagnetic
radiaton. See Video:
http://www.youtube.com/watch?v=WO38qVDGgqw
AGAIN…light, magnets and electricity are all one in the same
force!!!!
The Strong Nuclear Force
• This force works at extremely short range
within the nucleus
• Binds protons and neutrons together within
the nucleus.
• Keeps protons from repelling each other
• If disrupted, the energy released is
tremendous (example: Sun, nuclear bombs)
Summary of Forces:
http://www.youtube.com/watch?v=zdnmqbL4jp0
Lecture (10 minutes) on the four forces