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.
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.
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).
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?
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
90 km
hr
1000
1
m
km
1hr
60 min
1min
25 /
60m s
s
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?
• 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
Components of Vectors
If the components are perpendicular, they can be found using trigonometric functions.
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.
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
12
• 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
13
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
14
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
15
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
16
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
17
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.
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
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
20
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?
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?
