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 3 rd Law All forces are pairs of equal size and opposite direction Independent of anything

Momentum Momentum = mass x velocity Useful for understanding collisions 3 rd 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