Physics 321

Hour 1Course Introduction

Course Components• Course Outline• Prerequisites: ODEs, Mathematica• Reading: Due before lecture• HW: Due MWF - see schedule on Learning Suite• Take-home Tests: Due every other Thursday• Midterm Exams: In the Testing Center• Final Exam: In Class

Course Components• Reading: 5%• Homework: 10%• Take-home Tests: 40%• Midterms: 25%• Final: 20%

HW & Take-home Tests

Physics 321

Hour 1Newton’s Laws of Motion

Before NewtonWhat is the natural motion of an object?• Greeks – without force, motion stops• Kepler – straight lines (earth→heavens)• Galileo – circles (heavens →earth)• Descartes – matter and motion are conserved

Before NewtonHow do we understand collisions?• Descartes – conservation of motion• Huygens – motion = mass x velocity• Leibniz – vis viva = mass x velocity2

Newton’s 0th LawThe quantity of motion is the measure of the same, arising from the velocity and quantity of matter conjointly.

= Huygen’s definition of motion

Newton’s 1st LawEvery body continues in its state of rest, or of uniform motion in a right line, unless it is compelled to change that state by forces impressed upon it.

= Descartes’ idea of natural motion

Newton’s 2nd LawThe change of motion is proportional to the motive force impressed, and is made in the direction of the right line in which that force acts.

= A way to measure/define force

Newton’s 3rd LawTo every action there is always an equal reaction; or, the mutual actions of two bodies upon each other are always equal, and directed to contrary parts.

• Forces are binary• Momentum is conserved instant by instant• Forces add as vectors

Newton’s Laws and Measurement

What do we have to measure to verify/applyNewton’s laws of motion?

What is mass, space, time?

How have our ideas of mass, space and time changed since 1687?

Do Newton’s Laws Work?How could we tell if forces are really are binary?

Are they binary?

Two examples: charges and a bat, Lorentz force

What would be necessary for forces to be conserved instant by instant?