LESSON 3

PHYS LESSON 3 FOR
THURSDAY, JUNE 03, 2010

I Introduction

II Logistics: Seating, Syllabus, etc.

III Turn in Assignments Due: Homework 1, Essay 1, etc. and Return of Papers

IV Test 1

V Mind Game 1

VI Review of Lesson 2: Vector Physics/Motion

A. Vectors
1. Virtual arrow: magnitude (size) and direction

a. heads, tails

b. adding vectors ≠ adding algebraically

c. adding vectors

i. align the head of one vector with the tail of another; never put 2 tails together, or 2 heads

together: →→ is

okay; NOT →←

and NOT ←→

ii. →↑ is okay; but ↑→ is not okay; and →↑ is not okay
2. A vector usually has an arrow (→) above it: , or a “hat” or “carrot” (^) above it:

3. Pythagoras (576 BC – 495 BC)










4. Velocity, acceleration, force, momentum, or any number of other concepts can be represented as vectors
5. Components: see above; the x-component of vector A+B is A; the y-component is B.
6. If a vector is not directly along the x-axis or along the y-axis, it can be broken down into its x- and y- components
7. Acceleration vector, along an inclined plane: a = g sin θ, where θ is the angle shown:







8. Projectile Motion

















a. Range, height, angle (above)

Lesson 3: Circular motion
a. v = 2pr/P Э 2pr = c (circumference); r = radius; P = period, in seconds, to make one trip around the circle; and P = 1/n, Э n = the frequency in cycles per second (Hz).

b. v2/r = 4p2r/P2, but since P = (1/n), then P2 = (1/ n)2, or (1/P2) = n2


c. So, v2/r = 4p2rn2 which can be written as v2/r = (2pn)2 r

d. And, in circular motion, a = v2/r =
(2pn)2 r, “centripetal acceleration”
e. However, 2pn = w in rad/sec, thus a = w2r

f. If part of a circle, say, s, is the arc, AB, then we can say that for small “s” that r sinθ = s, and if it’s even smaller, then r θ = s because for small θ, sin θ = θr where the angle, θ, is measured in radians, not degrees. 360° = 2p radians, so 1 radian = 57.3°.

g. Since v = dist/time, then v = s/t = r (θ/t) but is another way of writing (θ/t) = w, so
v = wr and v2/r = w2r = a, “acceleration”

V Conclusion
A. HWK Assignment 2: handout. due 6/10
B. Essay 2: Sir Isaac Newton, due 6/10