# PSC 1121 Lecture Notes - Lecture 3: University Of Manchester

4 pages23 viewsSpring 2017

Department

Physical SciencesCourse Code

PSC 1121Professor

Thomas BruecknerLecture

3This

**preview**shows page 1. to view the full**4 pages of the document.**Physical Science

1.17.17

From recent reading in a traffic safety course

If speeding, stopping distance is greater

If you double your speed, distance required for braking will be four times longer

You’re more likely to skid or roll over in a turn.

Force of impact in collision is much greater.

By increasing speed by 10 mph to 35 mph, force of impact doubles

Universe not random

1. Galileo convinced that “grand book” of Nature was written in mathematical language

2. His program of study, the physical sciences,

a. Speaks in this language

b. As well as in English, Italian, etc.

c. Requires observation and measurements

d. And we are students in Galileo’s school!

Velocity, position, and distance

Discussed how to calculate a distance

From x-coordinates of positions A and B

v = x/t

x = xb – xa

t = tb – ta

Discussed how to calculate elapsed time

From clock readings at positions A and B

Used speed definition to get a speed

Also tried it on HW 1!

Let’s double-check HW 1 #3

Follow up about average velocity and instantaneous velocity

1. Average is based on

a. A finite number of position and time measurements

b. i.e., two “snapshots” in HW 1 example

2. But you don’t necessarily know what the guy did between t = 0.00s and t = 0.74s

a. He could’ve been same speed all the way,

b. Or could’ve taken a break, then sped back up

3. Same as tortoise and hare fable (Ch. 1-11)!

4. And the Turkey Lake Service Plaza example (p. 11, Ch. 1-10)

Avg. and Instantaneous Velocity

5. The tortoise and hare fable based on two dynamical ideas:

a. Once the tortoise gets going, his speed at any instant of time is same as what

will eventually be called his avg. speed;

b. The hare’s velocity state changes several times during his race

6. In terms of instantaneous speeds, v(t), pronounced “v of t”

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