1. Newtonian Mechanics

2.  Corpus omne persevare in status suo quiescendi vel movendi uniformiter in directum nisi quantenus illud a viribus impressis cogitur statum suum mutare.

3. Newton’s First Law  Every body continues in its state of rest or uniform motion in a straight line unless compelled by an external force to change that state.

4. Galileo and the Law of Inertia  Galileo looked at motion differently.  If you push an object across a surface, the smoothness or lubrication on the surface affects how hard you have to push the object to keep the object moving.  As the surface gets slicker and slicker, the force required gets smaller. Eventually, the force required to keep the object moving would decrease to zero. This leads to:

5. The Law of Inertia  The Law of Inertia states that a body once set in motion and thereafter undisturbed will continue in uniform motion forever, all by itself.  This can be simplified to, “An object continues doing what it is already doing.”

6. Newton add to the Law of Inertia  Newton used Galileo’s Law of Inertia as the basis for his first law that was published in his 1687 work, Principia Mathematical Principles of Natural Philosphy.  Newton extended this law with other laws of motion.

8. Newton’s Life  Born December 25, 1642  Gregorian calendar January 4, 1643 but it was not adopted until 1752.  Started Trinity College June 1661 and wanted to be a lawyer.  The plague closed Cambridge for two years starting in 1665. Newton did work at home.  Appointed to the Lucasian Chair in 1669.

9. More on Newton  1687 published Philosophiae Naturalis Principia Mathematica  1693 had a nervous breakdown  1696 appointed Warden of the Royal Mint  1699 appointed Master of the Royal Mint  1703 elected president of the Royal Society  1708 Knighted  1727 died

10. Inertia and Mass  So strong is our belief in the Law of Inertia, we try to use inertia reference frames.  Inertial reference frames are frames of reference where the Law of Inertia does work.  The rotating frame of reference is an example of a not inertial reference frame. Our minds start to create forces to explain apparent deviations from the expected motions.

11. A Word About Forces  Forces are defined as a push or pull on an object.  Forces are vector quantities.  In the Metric System of measurement, forces are measured in Newtons (N).  1 N = 1 kg ·m/s²

12. The Fundamental Forces  There are four fundamental forces in Nature. All other forces are really combinations of the four fundamental forces.  The four fundamental forces are:  Gravity  Electric-Magnetic Force  Strong Nuclear Force  Weak Nuclear Force

13. Force of Gravity  The force of attraction between any two masses.  This force is proportional to the product of the masses and is inversely proportional to the square of the distance between the masses.

14. Electric Force  The electric and the magnetic force are two different aspects of the same force.  The electric force can be an attractive or a repulsive force and depends on the charges involved and the distance between the charges.

15. Strong Nuclear Force  The strong nuclear force is the attractive force between two nucleons (neutrons or protons).  The strong nuclear force is responsible for holding the nucleus of an atom together.

16. Weak Nuclear Force  The weak nuclear force is a repulsive force that is responsible for radioactivity.

17. “Common” Forces  Normal Force  The force a surface exerts on an object.  The normal force is perpendicular to the surface.  Tension  The force that is exerted by a rope, string, cable etc. on an object.  Remember, you can’t push with a rope.  Elastic Force  The force exerted by stretching or compressing an elastic object.

18. More “Common” Forces  Friction  The force between two surfaces acting parallel to the surface.  Buoyancy  The force a fluid applies to an object due to differences in density.

19. Units of Force  In the SI system, forces are measured in Newtons (N).  A Newton is equivalent to a kilogram·metre/second².  1 N = 1 kgm/s²