scientific method

• technique of investigating phenomena that includes repeated cycles of:

• observation

• experimentation

• explanation & prediction

• review & reporting

• .

1

scientific terminology

• phenomenon: an observable event

• fact: objective verifiable observation

• hypothesis: tentative explanation

• theory: (next slide)

• .

2

scientific theories

• simple as possible

• accurately describe a large class of observations

• make definite predictions about future experiments

3

equilibrium

• Net force = 0

• Acceleration (change in speed or direction) = 0

• Rest and remains at rest

• Constant velocity

Force diagrams

• sketch

• “pull” from a “dot”

• Scale arrows for size & direction

Non-equilibrium

• Net force not equal to zero.

• Speed and/or direction of object changes

• Exs: free-fall, collision, inclined plane, car braking, accelerating, turning.

• Normal force, friction, general forces, weight

Newton 3rd Law

• All forces are pairs of equal size and opposite direction

• Independent of anything

Momentum

• Momentum = mass x velocity

• Useful for understanding collisions

• 3rd law implies no change in momentum

• Conserved when no other net action exists

Energy & Energy Transform

• Total energy always conserved

• Types: kinetic, potential (gravitational, spring, chemical)

• Energies transform (called work)

Elements

• Number of protons (1 = hydrogen, 2 = helium)

• Independent of # neutrons

• Protons are + charged

• Neutrons have no charge

• Electrons are - charged

Density, Archimedes

• Density = mass/volume

• Mass (grams, kg)

• Volume (1mL = 1cc)

• Water is 1g/cc

• Body immersed in fluid experiences buoyant force equal to weight of displaced water

Elasticity & Bending

• Hooke’s law (F ~ x)

• force ~ to deformation

• F = kx stiffness = F/x

Bernoulli

• Pressure of a moving fluid decreases with speed of fluid

Boyle’s Law

• Confined gas:

• Pressure inversely ~ to volume

• P ~ 1/V

• Think about billiard balls on pool table

Specific heat

• Amount of heat needed to raise temp of 1kg of substance by 1C.

Heat transfer

• Modes:

• Conduction (thru)

• Convection (by)

• Radiation (light)

Vibrations & waves

• Velocity = frequency x wavelength

• Review wave lab

• Resonant frequency of object ~ 1/length

• Objects emit & absorb well at resonant frequency

sound

• Describe sound waves

• Intensity = power/area

• Sound level (dB) non-proportional measure of intensity