SPH 4U1
Physics
Essential Skills

Reference: Appendices
Units are extremely IMPORTANT in this course. Always show them in your calculations.
Significant Digits
· Nonzero numbers are significant digits ( i.e. 23.4 has 3 sig. digits).
· Zeros before other digits are not significant (i.e. 0.0003 has 1 sig. Digits). Zeroes between other digits are significant (i.e. 20003 has 5 sig. Digits). Zeroes after other digits behind a decimal are significant (i.e. 70.00 has 4 sig. Digits).
Significant Digit Rules for Calculations
Multiplication and Division:
The answer will have the same number of significant digits as the measurement with the least number of significant digits.
Addition and Subtraction:
The answer will have the same number of decimal places as the measured value with the fewest decimal places.
Rounding:
· Always round off answers to the least # of decimals in the original measurements.
· If digit dropped is 4 or less leave preceding digit unchanged.
· Round up if digit dropped is > 5 or if it is a 5 followed by at least one nonzero digit (i.e. 7.751 rounds to 7.8).
· If digit to be dropped is a lone 5 or a 5 followed by zeros, the preceding digit is not changed if it is even, but is increased if it is odd (i.e. 6.675 rounds to 6.68 & 6.465 rounds to 6.46). In other words make the preceding digit even. AS PER NELSON TEXTBOOK
Know how to convert units to Base SI Units
Error Analysis (remember to apply in lab writeups) :
All counted quantities are exact. All measured quantities have a built in uncertainty which is determined by the measuring instrument. Scientists agree that the uncertainty in a measured quantity is ½ of the value of the smallest division on that instrument.
Example: A ruler with only cm divisions will have an uncertainty of
Accuracy/Reporting Error: Accuracy is how close a measured value is to the accepted value.
Absolute Error = Experimental Value – Accepted Value
% Error is more useful than absolute error
% Difference (% Deviation) is used in cases where the Accepted Value isn’t known so scientists compare trials.
Trial 
Time for 10 cycles(s) 
Time for 1 cycle (s) 
SOLVE Difference in values 
ANSWER % Difference (from trial 1) 
1 
20. 
2.0 


2 
21. 
2.1 
0.1 
5.0 % 
3 
22. 
2.2 
0.2 
10. % 
4 
20. 
2.0 
0.0 
0.0 % 
5 
18. 
1.8 
0.2 
10. % 
6 
19. 
1.9 
0.1 
5.0 % 
7 
20 
2.0 
0.0 
0.0 % 
Average of Values = 2.0