The Laws of Motion and Gravity Isaac Newton The Laws of Motion and Gravity

Isaac Newton 1642 to 1727; Lived during the last European plagues, the Baroque period in music, and the beginning of the Age of Reason. Thinkers who came after saw Newton’s Laws as a description of a Mechanical Universe.

Newton’s First Law of Motion: An object in constant motion in a straight line at a constant speed (or at rest) stays in motion in a straight line and constant speed unless acted upon by an external force. Radical departure from previous ideas of Aristotle who believed objects moved because of their own natural tendencies

Newton’s Second Law: The acceleration of an object is directly proportional to, and in the same direction as, the applied force, and is inversely proportional to its mass. In short, F = ma Force measured in Newtons, a kg m/s Weight is a force, not a kilogram.

Newton’s Third Law The Karma of Physics For every action there is an equal and opposite reaction. The action/reaction pairs occur at a single point. (you feel something you push on with a force equal to your pushing.)

Inertia A quality, not a dimensional quantity. Related to mass however. In Physics, inertia is a resistance to a change in motion, speed or direction. Combines all three Laws.

Friction If the laws of motion or kinematics seem to be in error, that’s because friction needs to be included. These simple ideas are ideals. Contact friction is the stickiness between surfaces. Fluid resistance is like air or water pressure as you move it. Terminal velocity: the fastest a object can fall in a viscous medium w/o addition force.

Momentum P = mv Always conserved! The momentum in a system before an interaction like a collision is the same as afterwards. Recoil Three kinds of collisions: elastic (a clean bounce), inelastic (bending and breaking occurs), and perfectly inelastic (objects stick together).

Gravity Every object in the universe attracts every other object with a force directly proportional to the product of the masses and inversely proportional to the square of the distance between their centers. G is a constant of proportionality