Transcript unit b Physics 2015x

And now for something
completely different
ask a ninja
The metric system is comprised of 7 base units :
1. metre - (unit of length)
Is the distance traveled by light in a
vacuum during a time interval of
1/2997294858th of a second.
2. kilogram - (unit of
mass) equal to the mass of
the international prototype
kilogram in Sevres, France.
3. second
- (unit of time)
based on the decay of a
cesium-133 atom.
4. Ampere - unit of electric current
5. Kelvin
- unit of temperature
6. candela - unit of luminous intensity
7. mole
- unit of amount of substance
Prefixes
To express larger or smaller amounts of these
base units, we use prefixes.
Working with prefixes:
Eg) convert
1.4 cm = _______________ m
Step 1: Find the prefix on your conversion chart.
3 x 108 m/s
6 370 000 m
6 370 km
Significant Digits
“The lost and puzzling art of the
ancient world”
• Okay, so there really isn’t anything strange or
puzzling about sig digs (or significant figures,
sig figs, are they’re also called by lesser
physicists), and I’m certain they weren’t
developed in ancient China.
• Sig digs is a system of rules used to
determine how many decimal places answers
should be rounded to.
• The system consists of two easy rules (which
will haunt you for the rest of your life!)
Determining the # of Sig Digs
• All digits in a number are significant.
This includes digits before and after the
decimal. Scientific notation does not
count.
• Examples:
–5
 1 sd
– 4.5
 2 sd
– 89.9  3 sd
– 3.4 x 10-7  2 sd
Zero Rule
• Zeros to the left of the first digit are only place
holders and do not count as sig digs.
• Zeros to the right of the first digit or inside values
count as sig digs.
• Examples:
– 0.005  1 sd
– 1.005  4 sd
– 0.0050001  5 sd
Practice:
• How many sig digs does each of the
following values have?
– 58.00
– 5.08
– 0.0085
– 1.054
– 5.00 x 109
– 0.001 x 105
What are not sig digs?
• sd do not include:
– Exact numbers
• The mass of 3 goats is 24.5 kg, what is the mass
of each goat...the 3 does not count as a sd.
– values from the data booklet
Operations with Sig Digs
• Adding or Subtracting:
Your answer should contain the same number of
digits after the decimal as the smallest
number of digits after the decimal in the
question.
Example:
4.5 + 7.85 + 6.98247 =
? _
Answer: 19.33247
But since the 4.5 has only 1 sd after the decimal, then
the answer must also only have 1 sd after the decimal..
Proper Answer: 19.3
Example:
5.4 – 3.24 =
? _
Answer: 2.16
But we must now change our answer to proper sd…
Since the question had, at least, 1 sd after the decimal, the
answer must only have 1 sd after the decimal.
Proper Answer : 2.2
Multiplying and Dividing Rule:
• When multiplying or dividing, you must
have the same number of sd in your final
answer as the least number of sd in your
question.
Example:
2.45 ÷ 1.432=
? _
Answer: 1.71089…
Proper Answer : 1.71
Example:
5.8 x 102 * 1.255 =
Answer: 727.9
Proper Answer : 7.3 x 102
? _
If you’re lost…
• Pages 132 of the Textbook.
Do assignment 1
https://www.youtube.com/watch?v=llRkf1fnN
DM
3.3 x 102 m/s
• Do assignment 2
https://www.youtube.com/watch?v=EkHTsc9P
U2A
1.80 km
46 m
e
• Do assignment 3
• Do lab 7 uniform motion
http://www.youtube.com/watch?v=emhxbwVy
N4w
38.5 m
0.0067 m/s2
Do assignment 4
Do assignment 5
Do lab
Review section 1
quiz
https://www.youtube.com/watch?v=HHYECUcf
C1Y&list=PL224464F48007F658
Do assignment 6
Do assignment 7
https://www.youtube.com/watch?v=GPJBwTLYZQ
Do assignment 8
Do lab
https://www.youtube.com/watch?v=0ca9rxQk
EiA&list=FLFh2qGd_dOAiaY5L4tkyeLQ
do assignment 9
Do lab
Review section 2
Quiz
Unit review
Unit exam