LESSON 2

PHYSICS LESSON 2 FOR
WEDNESDAY, JUNE 02, 2010

I Introduction

II Logistics: Seating, Syllabus, website:
http://drdaveupwardboundphysics.blogspot.com

III Review of Lesson 1: Measurements, Ch 1
A. Units – metric (mks; also known as SIU)
B. Meters for length
Length / Distance / Displacement, “x”
C. Kilograms for mass
Mass; 1kg = 2.2 lbs at sea level
D. Seconds for time
Time; second; 3600 sec = 1 hour
E. Coordinates: 3D: x, y, z
F. Speed: v = Dx/Dt; D = “change of” or
(x2 – x1) / (t2 – t1)
Velocity = speed with a vector
G. Acceleration = Dv / Dt or (v2 – v1) / (t2 – t1) ; often a vector
H. Scientific Notation:
5,617 = 5.617 x 103 or 5.617 x 10^3 or 5.617 E3
I. Significant Figures: 5,617 x 27 = 151,659 ? NO! 150,000 or 1.5 x 105
J. Estimating (ball parking; educated guessing): 5,617 x 321 = (5.6 x 3) x 105 = 16.8 x 105 = 1.68 x 106 for a guess. Exact is 1,803,057 = 1.80 x 106
K. Trigonometry: Create a right triangle inside a “unit” circle of radius r = 1. Then the x-component will be r cosine(θ) and the y-component will be r sine(θ) . However, since r = 1, we realize that the x-component will almost always be cosθ while the y-component will almost always be sinθ. Plus, sinθ / cosθ = y/x = tangent of the angle, or, tanθ.

IV 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. KISMIE
5. Velocity, acceleration, force, momentum, or any number of other concepts can be represented as vectors
6. Components: see above; the x-component of vector A+B is A; the y-component is B.
7. 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
8. Acceleration vector, along an inclined plane: a = g sin θ, where θ is the angle shown:


V Laboratory Exercise 2: Measurement


VI Conclusion
A. Finish Homework 1 Problems until end of period
B. Prepare for Test 1 (review and problems)