Scientific Method, Motion, Energy, Heat

1
Scientific Method, Motion, Energy, Heat

• Chapters 1 - 4

2
Scientific Method

• Must have common language (mathematics and metric
  system)
• Must have common standards (how we judge
  experiments, peer review)
• Cyclic process (hypothesis, experiment, repeat
  and rinse)

3
Numbers and Errors

• In science there are few absolute measured
  numbers. All have some error!
• Mass of a proton, size of a star, etc.
• Reporting numbers with errors critical (digits
  written represent measurements)

4
Models and Theories

• Almost all that we know that describes nature is
  just a model and an attempt to get at the reality
  but never reaching it
• Models are improved over time through experiments
  and refinement/new theories

5
Microwave Oven

• Push a button but what happens?
• Foot gets hot? How?
• Microwaves? What are they?
• Light absorbed by what?
• Water in food is made of what elements?
• How is energy stored as heat?
• Motion of molecules?

6
Motion

• Greeks and Aristotle
• Constant speed depending on mass/density/material
• Galileo
• Constant acceleration regardless of material
• ACTUALLY DID EXPERIMENTS (balls dropped and timed)

7
Acceleration versus Speed

• Speed is measure of instantaneous rate of travel
  (distance per time)
• Acceleration is measure of CHANGE in speed
  (distance per time squared)
• Constant Acceleration
• v v0 a t

8
Acceleration

• Where does it come from?
• Newton described three laws of motion
• Forces produce acceleration
• F m a
• Gravity is what we feel (and stars/planets)!
• Electricity and Magnetism for molecules!

9
Movement in a Microwave?

• The light applies a force to water molecules
• The force rotates them
• Rotating molecules bump into one another
• Bumping becomes heat

10
Energy

• Kinetic Energy
• Translation, Rotation, Vibration
• Potential Energy
• Gravitational, Electric, Magnetic, Nuclear
• Mass Energy (Einstein)

11
Foucault Pendulum

• Interconversion of Potential and Kinetic energies
• Lost energy returned to system with magnets (on
  top)
• Plane of pendulum motion appears to rotate
• 360 x sin(latitude) per day