1. Brian Hwang

2. Newton’s Three Laws of Motion  The laws explain the relationship between the net force on a body and its motion.  The three laws were presented through Issac Newton's book Philosophiæ Naturalis Principia Mathematica (Mathematical Principle of Natural Philosophy)

3. Philosophiæ Naturalis Principia Mathematica  The book was released on July 5th, 1687.  It is considered to be one of the most important scientific books.  It states Newton's laws of motion, Newton's law of universal gravitation, and a derivation of Kepler's law of planetary motion.

4. F=ma This simple equation can be used to explain the first two Newton’s laws of motion.

5. The First Law of Motion “ Lex I: Corpus omne perseverare in statu suo quiescendi vel movendi uniformiter in directum, nisi quatenus a viribus impressis cogitur statum illum mutare.”  It states that every object continues in a state of rest or in a state of motion at a constant speed along a straight line, unless it is compelled to change that state by a net external force.  A state of rest can be merely considered as a state of motion at a constant speed of zero along a straight line.

6. The First Law of Motion (Cont.)  The first law is also known as the Law of Inertia. *Inertia – resistance to acceleration. (Inertia is proportional to mass)  F= ma -> a = F/m This demonstrates that the acceleration is directly proportional to the net force.

7. The Second Law of Motion “ Lex II: Mutationem motus proportionalem esse vi motrici impressae, et fieri secundum lineam rectam qua vis illa imprimitur.”  The second law is the most important law of the three laws.  It states that When a net force (ΣF) acts on an object of mass (m), the acceleration (a) that results is directly proportional to the net force and has a magnitude that is inversely proportional to the mass. The direction of the acceleration is the same as the direction of the force.  This law states the formula F=ma

8. Example of the Second Law  For example, if one flicks a small pebble, the pebble will bounce away. That means the pebble accelerated at a high rate.  However, if one flicks a huge, heavy rock, it will hardly move away. That means the rock accelerated at an insignificantly slight rate.

9. SI Unit Newton  From the second law, the unit of force N (Newton) can be derived.  F = m*a = kg * m/s 2 = N  The unit is the amount of net force required to accelerate a mass of 1 kilogram at a rate of 1 meter per second squared.

10. The First and Second Law  Now, if we look back at the first law, we see that the first law is just a special case of the second law when ΣF is zero. ΣF = m*a (2 nd law) 0 = m*a m is always bigger than 0 soa = 0 when ΣF= 0 (1 st Law)

11. The Third Law “Lex III: Actioni contrariam semper et æqualem esse reactionem: sive corporum duorum actiones in se mutuo semper esse æquales et in partes contrarias dirigi.”  It states that whenever a body exerts a force on a second body, the second body exerts an oppositely directed force of equal magnitude on the first body.  Simply “Equal and opposite”

12. Example of the Third Law  When one runs into someone who weighs just as much, both will bounce off to opposite direction but the same distance.  However, if one runs into someone who weighs much more, the one will bounce off further (F=m a ) in one direction than the heavier one who will bounce off less far (F= m a) to the other direction.

13. Conclusion  The Newton’s three law of motion is one of the most important and interesting topics in Physics.  The laws might be simple and seem like common senses per se.  However, the connections they have with the real world make it much more valuable and essential.  The laws explain the scientific view of the world: how things move, where things move to, and how far things move.

14. Conclusion (Cont.)  I look at my desk and see everything is at rest and now, I know it is because there is no net external force such as me pushing them or wind blowing onto them--Newton’s first law of motion.  Now, I push a ball. It moves and stops. It would move forever in the same direction at a constant speed if there was no other force such as friction--- Newton’s second law.  I am currently sitting on a chair. I would be falling down to the center of the Earth if the chair and the ground were pushing me back up---Newton’s third law.

15. As I now notice, Newton’s law of motion is everywhere.

16. Citation  http://csep10.phys.utk.edu/astr161/lect/history/ newton3laws.html http://csep10.phys.utk.edu/astr161/lect/history/ newton3laws.html   http://hyperphysics.phy- astr.gsu.edu/hbase/newt.html http://hyperphysics.phy- astr.gsu.edu/hbase/newt.html   http://www.grc.nasa.gov/WWW/K- 12/airplane/newton.html http://www.grc.nasa.gov/WWW/K- 12/airplane/newton.html   http://en.wikipedia.org/wiki/Philosophi%C3%A 6_Naturalis_Principia_Mathematica http://en.wikipedia.org/wiki/Philosophi%C3%A 6_Naturalis_Principia_Mathematica 