Physics

• Einstein, atomic bombs, spacecraft, math

• Baseballs, roller coasters, toasters, rainbows, cats

• The study of the physical world, the most fundamental of the sciences.

• The behavior and structure of matter.

• Hypothesis- a conjecture to be used as a basis for further investigation

• Theory- a synthesis of a large body of information that encompasses well-tested and verified hypotheses

• Fact- close agreement by many competent observers of the same phenomenon.

• Law- a concise statement about how nature behaves

The metric system

The System Internationale, SIStandards of length, time, and massLength: meter, mTime: second, sMass: kilogram, kg

Derived units: a combination of fundamental units, such as meter per second, m/s

Measurement uncertainties

Precision:

the degree of exactness, is limited by the divisions on the scale

Accuracy:

how well the measure agrees with an accepted standard.

Good measurements

Parallax, the apparent shift in the position of an object when it is viewed from different angles.

Scientific Notation and Rounding356,000,000,0003.56 x 1011

0.00000000033 x 10-10

2385674892.38 x 108

When moving the decimal point, the exponent changes: Left – Larger Right- Reduced

53.45678253.46

• It’s 1500 miles to Fresno, California

• ….EXACTLY 1500 miles???

• Which numerals are significantly important in the measurement of a quantity?

The rules for Significant Digits1. All non-zero digits are significant.

2. All zeros are significant unless the zeros are at the beginning of a numeral.

Examples:

238 23.0

2370 0.48

200250 0.00562

0.24020 10000 ? Put in scientific notation!

Graphing Data

Independent axis: the x-axis- horizontal

Dependent axis: the y-axis- vertical

The y values depend on the x values

Graphing Data

Linear relationship,y = mx + b

Inverse relationshipy = b/x, b = rational

number

Quadratic relationshipy = bx2

Linear Motion• Position- the location of an object relative to a

reference point. We often use the letter x to represent position. (“x marks the spot” Sometimes we also use “d”, when position is

some measured distance, d, from a reference point.

• Reference point- the point from which measurements are made.

Distance- how far something moves.

Displacement – how far something moves in a given direction.

(It’s only concerned about where you started and where you stopped, not what you did in between.)

For example: if you take a trip all the way around the world and end up right back where you started, you traveled a great distance, but your displacement was

zero!

Negative??

• Rate- a quantity divided by time- how much something is changing in a certain amount of time

• Speed- the rate at which position changes-

• “how fast?” Example: 60 miles per hour- the position of a car will change 60 miles in one hour. We will use m/s most often.

• Average speed =total distance covered ÷ time interval

• Instantaneous speed- the speed at any instant

- “delta”- a symbol that means “the change in”

the change in position, x Change in time, t Change in velocity, v

The change in a value is the difference between the final value and the original value- “final minus original”

velocity = final velocity – original velocityExample: a car was moving at 18 m/s and

then sped up to 22 m/s. What was v ? v = 22 m/s - 18 m/s = 4 m/s

Speed and Velocity

In physics, speed and velocity are not the same!

Speed is “how fast”,

Velocity is “how fast and in what direction”.

Example: 10 m/s is a speed,

10 m/s north is a velocity

“uniform” means “constant, unchanging”

At a uniform speed, the distance traveled is given by

Distance = speed x time

At uniform velocity, the displacement is given by

Displacement = velocity x time

d = vt

Examples

• How far will you go while traveling at 23 m/s for 12 seconds?

d = vt

= 23 m/s x 12 s =

276 m

• How long will it take to travel a distance of 240 km traveling at 12 m/s?

Convert 240 km to meters first!

240 km x =

240000 m

Rearrange the equation d = vt to solve for t

t = d ÷ v =

240000 m ÷ 12 m/s =

20000 s

km1

m1000

• How far, in meters, will you go while traveling at 70 km/h for 18 seconds?

• Convert to the 70 km/h to m/s first, then calculate the distance.

70

= 19.4 m/s

d = vt =

19.4 m/s x 18 s =

349 m

h

km

km1

m1000

s3600

h1

Graphing Motion

The velocity of an object can be found by determining the SLOPE on a position-time graph.