physicsmr. baldwin review10/4/13
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PHYSICSMR. BALDWIN REVIEW10/4/13. Aim : What have we done so far? Let’s review. Do Now : Please take out your notebooks and make a list of what we have done so far? HOMEWORK: Prepare for TEST on Monday 10/7/13. A brief review sheet will be posted online. - PowerPoint PPT PresentationTRANSCRIPT
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PHYSICS MR. BALDWINREVIEW 10/4/13
Aim: What have we done so far? Let’s review.
Do Now: Please take out your notebooks and make a list of what we have done so far?
HOMEWORK:
Prepare for TEST on Monday 10/7/13.
A brief review sheet will be posted online.
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1. Rules of Significant figures.
2. Scientific and decimal notation
3. 7 basic Units of measurement
4. Precision & Accuracy
5. Order of magnitude
6. Unit conversions between metric and BEU; between metric
7. Scalars and vectors– Definition & Components of vectors
– Examples of both: Speed, distance, and time are scalar quantities; Velocity, displacement and acceleration are all vectors.
8. Making line graphs
9. Constant and accelerated motion.
10. Freefall Motion
11. Distance & velocity-time graphs.
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7 Basic Units of Measurement
In Physics, we will be working in the SI system, where the basic units are kilograms, meters, and seconds (m.k.s).
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METRIC PREFIXES revised
These are the standard SI prefixes for indicating powers of 10.
CHECK
Can you give any common everyday examples where these prefixes are used?
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Section Check
A car is moving at a speed of 90 km/h. What is the speed of the car in m/s? (Hint: Use Dimensional Analysis)
Question
A. 2.5×101 m/s
B. 1.5×103 m/s
C. 2.5 m/s
D. 1.5×102 m/s
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90 km
hr
1000
1
m
km
1hr
60 min
1min
25 /
60m s
s
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Order of Magnitude: Rapid Estimating
A quick way to estimate a calculated quantity is to round off all numbers to one significant figure and then calculate. Your result should at least be the right order of magnitude; this can be expressed by rounding it off to the nearest power of 10.
Section Check
Calculate approximately how many basketballs (diameter = 75cm) can fit in this classroom randomly
AND orderly stacked one atop the other?
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• Accuracy: • How close you are to the
actual value
• Depends on the person measuring
• Calculated by the formula:
% Error = (YV – AV) x 100 ÷ AV
Where: YV is YOUR measured Value & AV is the Accepted Value
• Precision: • How finely tuned your
measurements are or how close they can be to each other
• Depends on the measuring tool
• Determined by the number of significant digits
Accuracy & Precision
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Components of Vectors
If the components are perpendicular, they can be found using trigonometric functions.
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Addition of Vectors: ResultantFor vectors in same or
opposite direction, simple addition or subtraction are all that is needed.
You do need to be careful about the signs, as the figure indicates.
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Recall• Graphs are made using pairs of numbers (x,y). • independent variables are plotted on the x-axis. • dependent variables are plotted on the y-axis.• Range is the difference between smallest and
largest value for a variable• Scale determined by dividing the range by the
number of data points and rounding off to the nearest integer.
• Titles must be give to graph &placed on both axes
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• Uniform motion refers to motion that has a constant velocity– Speed & direction remains the same– Such as your car on cruise control– Moving at 50 mph on a straight road
• Accelerated motion refers to motion with changing velocity– As you round a curb– Hit the gas or brake
Uniform & Accelerated Motion
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Average Speed & Instantaneous Speed• The instantaneous speed is the speed as given on your speedometer. The speed at that instant.
•Speed given by the speedometer
dv
t
• The average speed is the total distance traveled by an object divided by the total time taken to travel that distance.
CHECK: Determine the units
Unit: m/s; km/h; mph
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CHECKCHECK: : Can you write other forms Can you write other forms of the equation to determine the other of the equation to determine the other
two quantities two quantities tt & & dd??
dt =
d
=t
d v t
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AccelerationAcceleration is the change of velocity divided by time.
f iv va
t
Unit: m/s2Determine its Unit.
Where a: acceleration; vf: final velocity; vi:initial velocity
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Equations of Motion
2
2 2 2 2
For Uniform (Constant) Motion, we use
; OR
For Accelerated Motion, we use
OR
1
2
2 OR 2
f if i
i
f i f i
d dv t d v t
t v
v vv v at a
t
d v t at
v v ad v v ad
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Uniformly Accelerated Motion
Galileo’s Law of Freely Falling Bodies:
In the absence of air resistance, all objects, regardless of size, shape or mass, fall with the same acceleration.
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180
5
10
15
20
25
0 1 2 3 4 5
Finding Speed: What can you say about the slope of the graph at any time?
The slope of the tangent to the distance-time graph at any point is the instantaneous speed at that point.
4.00 m/s
8.00 m/s
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19
0.00
2.00
4.00
6.00
8.00
10.00
0.00 1.00 2.00 3.00 4.00 5.00
TIME (s)
SP
EE
D (
m/s
)Speed-Time Graph of Uniformly Accelerated Motion
f iv v at Slope gives acceleration of the body at each point.
4.00 m/s
2.00 s
Slope 2.00 m/s2
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Graphical Analysis of Linear Motion
The area beneath the velocity-time graph gives you the Distance travelled
CHECKHow would you find the area under the velocity-time graph?
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TEST YOURSELF…WHAT DO YOU UNDERSTAND? SCIENTIFIC & DECIMAL NOTATION
How do you write a decimal in scientific notation?What is the form?
METRIC PREFIXES
What are the metric prefixes?What values do the symbols represent?
MOTION
What is motion?How do you measure motion?
SCALARS & VECTORS
What is a Scalar?What is a Vector?Give some examples of both scalar and vector quantities.
VELOCITY
What is Velocity?What is the formula for Velocity?What is the Unit?Is it a Scalar or Vector?
ACCELERATION
What is Acceleration?What is the formula for acceleration?What is the unit for acceleration?