1. Motion in One Dimension
Reminder: Homework due on Wed, August 29
Converting Units
Order of magnitude
2.1 Reference Frame
2.2 average Velocity

2. Reading Significant Figures
Nonzero Digits are always significant
Zeros between significant figures are significant.
Examples:
409.8 s cm
950.0X 101 mL

3. Answer In 409.8 s : all four digits are significant
In cm: the two zeros on the left are not significant, they are used to place a decimal point, the numbers 5,8,7 are significant, and so are the two final zeros.
In X 101 ml: the final zero is significant since it comes after the decimal point. The zero at its left is also significant since it comes between two other significant digits, so the results is four significant figures.

4. Adding Significant Figures
67.9 g g g = ?
Sum (or difference) can’t be more precise than least precise quantity
Answer: 71.4 g
When you add or subtract you keep the decimal place of the least precise value.

5. Multiplying Significant Figures
Distance = velocity x time
Velocity = 65.4mph
Time = 4.2 hours
Distance=274.7 or 275 or 2.7x102 miles
When you multiply (or divide) you keep the number of significant figures that are equal to the quantity with the smallest number of significant figures.

6. Importance of Units The 165 million dollars Mars Polar Lander
Units help you figure out equations
Speed in mph
Density in kg/m3
Units help you determine the correct solution

7. Units, Standards, and the SI System
Quantity
Unit
Standard
Length
Meter
Length of the path traveled by light in 1/299,792,458 second
Time
Second
Time required for 9,192,631,770 periods of radiation emitted by cesium atoms
Mass
Kilogram
Platinum cylinder in International Bureau of Weights and Measures, in Paris

8. Units, Standards, and the SI System
Figure 1-5. Caption: Some lengths: (a) viruses (about 10-7 m long) attacking a cell; (b) Mt. Everest’s height is on the order of 104 m (8850 m, to be precise).

9. Units, Standards, and the SI System

10. Units, Standards, and the SI System

11. Units, Standards, and the SI System
We will be working in the SI system, in which the basic units are kilograms, meters, and seconds. Quantities not in the table are derived quantities, expressed in terms of the base units.
Other systems: cgs; units are centimeters, grams, and seconds.
British engineering system has force instead of mass as one of its basic quantities, which are feet, pounds, and seconds.

12. Converting units
Problem 11.(I) Write the following as full (decimal) numbers with standard units: (a) mm, (b) 35mV,
(c) 760 mg, (d) 60.0 ps, (e) 22.5 fm, (f) 2.50 gigavolts.

13. 1yd=3ft and 1m=3.28ft Converting units
Problem 15. (II) What is the conversion factor between (a)
ft2 and yd2 (b) m2 and ft2
1yd=3ft and 1m=3.28ft

14. Converting units Write this in miles/s and miles/hour 30.0 km/h =?
1 km = miles
1 mile=1.6093km
How many Us dollars is in 220 Canadian dollars?
$220 Canadian Dollars = ?
1 US dollar = 1.31 Canadian dollar

15. Converting units

16. Question 1 atm = 1.013 x105 Pa = 14.70 lb/in2
If you want to convert 0.46 atm to Pa you should
Multiply 0.46 atm by lb/in2
Multiply 0.46 atm by x105 Pa
Divide 0.46 atm by lb/in2
Divide 0.46 atm by x105 Pa 16

17. Converting units Multiplying by 1 leaves a quantity unchanged.
“1” can be represented as
Choose form for ‘1’ for which units match.

18. Prefixes Prefixes correspond to powers of 10
Each prefix has a specific name
Each prefix has a specific abbreviation

19. Prefixes The prefixes can be used with any base units
They are multipliers of the base unit
Examples:
1 mm = 10-3 m
1 mg = 10-3 g

20. Fundamental and Derived Quantities
In mechanics, three fundamental or base quantities are used
Length
Mass
Time
Will also use derived quantities
These are other quantities that can be expressed as a mathematical combination of fundamental quantities

21. Density Density is an example of a derived quantity
It is defined as mass per unit volume
Units are kg/m3

22. 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.
Diagrams are also very useful in making estimations.

23. Order of Magnitude: Rapid Estimating
Example 1-6: Thickness of a page.
Estimate the thickness of a page of your textbook. (Hint: you don’t need one of these!)
Figure 1-8. Caption: Example 1–6. Micrometer used for measuring small thicknesses.
Answer: Measure the thickness of 100 pages. You should find that the thickness of a single page is about 6 x 10-2 mm.

24. Chapter 2: Kinematics in one Dimension
Coordinate Axis
In Physics we draw a set of coordinate axis to represent a frame of reference.
In one dimensional axis coordinate, the position of an object is given by its x or y. y -x x o -y

25. Position on a line Reference point (origin) position Distance
Direction
The position of Charlotte in reference to Fort Mill ( Fort Mill is the origin)
Symbol for position: x
SI units: meters, m

26. Displacement on a line Change of position is called Displacement:xf xi
Displacement is a vector quantity
It has magnitude and direction

27. Displacement
Defined as the change in position during some time interval
Represented as x
SI units are meters (m) x can be positive or negative
Different than distance – the length of a path followed by a particle.
Displacement has both a magnitude and a direction so it is a vector.

28. Example
Mary walks 4 meters East, 2 meters South, 4 meters West, and finally 2 meters North. The entire motion lasted for 24 seconds. Determine the displacement and distance Mary travelled.

29. Vectors and Scalars
Vector quantities need both a magnitude (size or numerical value) and direction to completely describe them
Will use + and - signs to indicate vector directions
Scalars quantities are completely described by magnitude only

30. Average Speed Average speed =distance traveled/ time elapsed
Example: if a car travels 300 kilometer (km) in 2 hours (h), its average speed is 150km/h.
Not to confuse with average velocity.
Average speed is a scalar

31. Average Velocity
The average velocity is rate at which the displacement occurs
The SI units are m/s
Is also the slope of the line in the position – time graph

32. Average Velocity, cont Gives no details about the motion
Gives the result of the motion
It can be positive or negative
It depends on the sign of the displacement
It can be interpreted graphically
It will be the slope of the position-time graph

33. Not to Confuse Speed is a number : a scalar
Velocity is a vector : with a magnitude and a direction