How People Learn

Conclusion 1: Henri Poincaré “We must, for example, use language, and our language is necessarily steeped in preconceived ideas. Only they are unconscious preconceived ideas, which are a thousand times the most dangerous of all.”

“Birds,” said the frog mysteriously. “Birds!” And he told the fish about the birds, who had wings, and two legs, and many many colors.

“Cows,” said the frog. “Cows! They have four legs, horns, eat grass and carry pink bags of milk.”

“And people,” said the frog. “Men, women, children!” And he talked and talked until it was dark in the pond.

Conclusion 2: Expert vs. Novice Learners Conclusion 3: Metacognition or reflection

1600 to 1900 Classical Physics Mechanics Thermodynamics Electromagnetism 1900 to 1940 Modern Physics Relativity Large speeds (  10 8 m/s). Quantum Mechanics Very small scales (  m) to present Current Physics Particle Physics Cosmology Ch1-1 Physics and the Laws of Nature

How Physics Works Model / Theory Observation / Experiment

Length [L] meterDistance traveled by light in vacuum in 1 / seconds Mass [M] kilogramMass of a platinum-iridium alloy kept in France at the International Bureau of Weights and Measures Time [T] second times the period of vibration of radiation from the Ce-133 atom Ch1-2 Units of Length Mass and Time Standards

Ch1-2 Standards of Length Mass and Time Standards A Force acts on a mass resulting in motion. M L,T

Distance from the Earth to the nearest large galaxy (the Andromeda Galaxy, M31) 2 x m Diameter of our galaxy (the Milky Way)8 x m Distance from the Earth to the nearest star (other than the Sun) 4 x m One light year9.46 x m Average radius of Pluto’s orbit6 x m Distance from Earth to the Sun1.5 x m Radius of Earth6.37 x 10 6 m Length of football field10 2 m Height of a person2 m Diameter of a CD0.12 m Diameter of the aorta0.018 m Diameter of the period in a sentence5 x 10 –4 m Diameter of a red blood cell8 x 10 –6 m Diameter of the hydrogen atom10 –10 m Diameter of a proton2 x 10 –15 m Ch1-2 Standards of Length Mass and Time Typical Lengths

Scales

Galaxy (Milky Way)4 x kg Sun2 x kg Earth5.97 x kg Space Shuttle2 x 10 6 kg Elephant5400 kg Automobile1200 kg Human70 kg Baseball0.15 kg Honeybee1.5 x 10 –4 kg Red blood cell10 –13 kg Bacterium10 –15 kg Hydrogen atom1.67 x 10 –27 kg Electron9.11 x 10 –31 kg Ch1-2 Standards of Length Mass and Time Typical Masses

Ch1-2 Standards of Length Mass and Time Typical Times Age of the universe5 x s Age of the Earth1.3 x s Existence of human species6 x s Human lifetime2 x 10 9 s One year3 x 10 7 s One day8.6 x 10 4 s Time between heartbeats0.8 s Human reaction time0.1 s One cycle of a high-pitched sound wave5 x 10 –5 s One cycle of an AM radio wave10 –6 s One cycle of a visible light wave2 x 10 –15 s

10 15 petaP teraT 10 9 gigaG 10 6 megaM 10 3 kilok 10 2 hectoh 10 1 dekada 10 –1 decid 10 –2 centic 10 –3 millim 10 –6 micro  10 –9 nanon 10 –12 picop 10 –15 femtof PowerPrefixAbbreviation Ch1-2 Standards of Length Mass and Time Common Prefixes

Concept Question 1.1 (2.44 x ) / (2 x 10 3 ) = a.2.44 x b.2.44 x c.1.22 x d.1.22 x 10 2 e.1.22 x 10 8

Distance[L] Area[L 2 ] Volume[L 3 ] Velocity[L]/[T] Acceleration[L]/[T 2 ] Energy[M][L 2 ]/[T 2 ] QuantityDimension Ch1-2 Standards of Length Mass and Time Dimensions of Some Common Physical Quantities

Concept Question 1.2 Ch1-3 Dimensional Analysis Given the following definitions with their dimensions: v = velocity (L/T) a = acceleration (L/T 2 ) t = time (T) Which of the following equations could be correct as far as dimensions are concerned? A.v = at 2 /2 B.v = a/2t C.v = at D.v = a 2 t/2 E.v = a/t 2

How does v depend on a and x? P1.5 (p. 14) Suppose v 2 = 2ax p What is p? Ch1-3 Dimensional Analysis

Concept Question 1.3 Which statement is correct regarding significant figures? A = B – 1.3 = 0.18 C / 1.5 = D.1.5 x = E x 1.5 = 0.23 Ch1-4 Significant Figures

Do P1.12 (p. 14) P = 2 l + 2 w Ch1-4 Significant Figures

Round-off: If next digit is  5, then round up. Scientific Notation: Covered previously. Ch1-4 Significant Figures

Concept Question 1.4 How many seconds in a 50 minute class period? A.1000 B.50 C.3 x D.4500 E.3 x 10 3 Ch1-5 Conversion of Units

Do P1.24 (p. 15) Ch1-5 Conversion of Units

CT1.5 A. 500 B. 5,000 C. 50,000 D. 500,000 Ch1-6 Order-of-Magnitude Calculations

Shea Stadium holds about 55,000.

CT1.6 Donovan Bailey – Canada – 1996 Olympics Who is in 0.1 s of Donovan? A. 2,3,4,5 B. 2,3,4 C. 2,3 D. 2

Donavan is roughly 2 meters tall and that gives the scale. Since they covered 100 m in 10 seconds, each meter takes about 0.1 seconds. The answer is c because they are within roughly 1 meter (half Donovan’s height).

Estimate how many barbers in Chicago?

I started by assuming a typical person gets a haircut every two months. Next I assumed that a barber could give about 4 haircuts/hr or 20/day or 100/week or 400/month or 800/every two months. I rounded this off to about 500/every two months since there may be times when the barber doesn't have customers. So a barber could take care of about 500 customers and then they would all come back again. There are about 3 million people in Chicago proper and 8 million in the metropolitan area so I picked an average of 5 million to represent Chicago. That means about 5x10 6 / 500 or 10 4 or 10,000 barbers. This is just an estimate and may be off by a factor of 10 either way given all the questionable assumptions!

A Google search listed 1711 barbers around Chicago.

Ch1-7 Scalars and Vectors A scalar is a pure number. What are some examples? A vector has magnitude (value) and direction. What are some examples? The magnitude of a vector could be considered a scalar.

Ch1-8 Problem Solving Read the problem carefully. Sketch the system. Visualize the physical process. Strategize. Identify appropriate equations. Solve the equations. Check your answer. Explore limits and special cases.

Ch1-8 Problem Solving Do P1.39 (p. 16) N = number of beats B = beats/second T = time

Mechanics Study of forces and energy and motion. Force is an agent of change. Energy is a measure of change.