Introduction to Motion and Gravity

Introduction to Motion and Gravity

Galileo Galilei 1564- 1642 • Classic legend describes Galileo dropping rocks off the leaning tower of Piza to understand gravity better • While this is a cultural myth, Galileo did investigate gravity using logic

Sir Isaac Newton 1642 - 1727 • Hides from the plague as a 17 year old on his aunt and uncle’s estate • In solitude he invents calculus • He also is the first to quantify gravity

Newton • Cultural myth has Newton thinking under an apple tree. An apple hits his head and he starts thinking about why the apple fell down instead of up.

Three Laws of Motion • An object at rest tends to stay at rest, an object in motion tends to stay in motion unless acted upon by an unbalanced outside force. (Law of Inertia) • The acceleration of an object is proportional to the amount of force applied to it and inversely proportional to its mass. • For every action, there is an equal and opposite reaction.

Law of Gravity • Every mass exerts a force of attraction on every other mass. The strength of the force is directly proportional to the product of the masses divided by the square of their separation distance. Fg = gravitational force M = mass of first body m = mass of second body r = distance between bodies’ centers (G=6.67 x 10-11 m3/kg●s2)

Albert Einstein 1875- 1955 • Describes gravity as a non-instantaneous force • Gravity explained in his “rubber sheet theory” of a 4D space- time continuum • Einstein’s focus was on describing TIME not gravity

Gravity is one of four fundamental forces • (Nuclear) Weak • (Nuclear) Strong • Electromagnetic • Gravity

In the beginning • At the time of the Big Bang, all four forces were “unified” as one force • First, Gravity broke away leaving the other three as what is known as the “GUT” force (Grand Unified Theory) • Next, the strong force broke away leaving the “electroweak” force. • Finally, the electromagnetic and weak forces split, leaving the four we know today.

In the beginning • All of these splits happened within 10-10 seconds after the Big Bang • Scientists are still trying to reconcile these four forces using different theories.

Gravity is a property of all objects that have mass Gravity has an infinite affect throughout the universe Gravity is a force A force is a push or a pull on an object Gravity is a pulling force What is gravity?

Force is determined by the mass of an object and its acceleration F = m x a The force of gravity is not consistent over the face of a planet Weight is a measure of how a planet pulls on your mass YAY, Math!

In the English system mass is measured in slugs, weight is measured in pounds In the metric system mass is measured in grams, but force (weight) is measured in Newtons (kg-m/s2) Weight is a Force, Mass is not

Acceleration is determined by change in speed in a certain amount of time A = Ds / Dt The symbolD means change in and is read “delta” Change is found but subtracting initial from final Ds = sf - si Acceleration

The Equation • A = DS = Sf – Si Dt tf – ti F = m x a = m DS = m x (Sf – Si) Dt tf – ti

Introduction to Motion and Gravity