Physics Review

What do I need to know???

Variables

• Definition• Types– Independent– Dependent

Graphing

• Parts of a graph– Axis labels• Variables that go on each label

• Getting a straight line– y = mx + b• m = slope• b = y intercept

GraphingTime Distance

0 s 0 m

5 s 15 m

15 s 45 m

If you are given data….Graph it and then find the slope and intercept of the line

Pendulum Experiment

• Possible Variables– Length– Mass– Angle

• IV = your chosen variable• DV = time (pendulum period)• Variables that actually changed the period– Length

Pendulum Equation

• I will give it to you…• Remember how to use it– What is the period of a pendulum with a length of

2 m?

– What is the length of a pendulum that has a period of 2 seconds?

Vector vs. Scalar

• Scalar– Just a number, no direction.– Examples

• Speed

• Vector– Has both a direction and a magnitude.– Takes into account the direction and the magnitude.– Examples

• Acceleration and velocity

Speed

• Equation for speed– Speed = Δd/Δt

• A person walks 400 m in 2 minutes. What is their speed in m/s?

• How far does a person run if they walk at 7 mi/hr for 55 minutes?

Speed Calculations

• Speed is…– Total distance traveled = 27 + 14 = 41 miles– Total Time = 33 minutes = 0.55 hours– Speed = 41 miles / 0.55 hrs = 75 mi/hr

Yuma Eckley Wray

14 miles in 10 minutes

27 miles in 23 minutes

Velocity

• Equation for Velocity– Δd/Δt• but…you have to take into account the direction

• Two types– Instantaneous• At one specific time.

– Average• Over a period of time

Velocity Calculations

• Velocity is– Δd = 13 miles East– Δt = 41 minutes = 0.55 hrs– V = 13/ 0.55 = 24 mi / hr EAST

Yuma Eckley Wray

14 miles in 10 minutes

27 miles in 23 minutes

Finding Velocity From a Graph

• Velocity is from the position vs. time graph.

0 5 10 15 20 25 300

5

10

15

20

25

30

Position

Time (s)

Positi

on (m

)

Find the average velocity… For 0-25 seconds

For 0-10 seconds

Find the instantaneous velocity for…10 seconds

20 seconds

Acceleration

• Definition and Equation– ΔV /Δt

• Types– Instantaneous– Average

Finding Acceleration From a Graph

• Velocity is from the velocity vs. time graph.

Find the average acceleration… For 0-15 seconds

For 10-20 seconds

Find the instantaneous acceleration for…10 seconds

20 seconds

0 5 10 15 20 25 300

5

10

15

20

25

30

Velocity

Time (s)

Velo

city

(m/s

)

How all the graphs relate

• On the board…

Significant Figures

• Know the rules– Before the numbers

• Doesn’t Count

– Between the numbers• Always Counts

– After the Numbers• After the decimal

– Always counts

• Before the decimal– With a decimal (counts)– Without a decimal (doesn’t count)

Significant figures and Calculations

• The lower number of significant figures determines how many sig figs are in the answer

0.0090 x 100. =

100.0 x 12 =

3.00 x 0.002 =

Significant Figures and Sci. Notation

• Only significant numbers appear in the number part of scientific notation.

0.900 =

2.00 x 10. =

4.00 x 140 =

Metric

• Know the prefixes– Kilo, hecto, deca, deci, centi, milli

100 cm = _______ hm

1 kg = ________ cg

Conversions

• Always start with what you know over 1• Include Units• Remember, if you want units to cancel out you

have to have one on top of the fraction and one on the bottom of the fraction

1 mile = __________ inches

3 ft = __________ miles