3.1A Measurements and Their Uncertainty Chapter 3 3.1A Measurements and Their Uncertainty

Measurement… Number Unit Fundamental to the experimental sciences Units in science = International System of Measurements (SI)

Scientific Notation Scientific notation is an easier way to express a very small or very large number.

The coefficient (first number) must always be less than ten. The exponent depends on how many decimal places you must move.

Scientific Notation Continued For example, 26,000,000,000 would be written as 2.6 X 1010. Any number smaller than 1 would get a negative exponent (ex. 0.00000000352 = 3.52 X 10-9).

Need More Help?? Pg. R56 of Appendix C

Rounding Five or more, raise the score… Four or less, let it rest… Round the following to TWO decimals: 5.46783 8.23498 -1.4909 X 10-2

Accuracy How close a measurement comes to the TRUE value.

Precision How close measurements are to one another.

Percent Error Accepted Value: “Correct Value” Experimental Value: Value you measured in your experiment (you weighed it) Absolute Value: Makes the value positive

Percent Error Calculation Error = experimental value – accepted value % Error = (|Error|/Accepted Value) X 100 Taking the absolute value of the error (top) always gives you a positive answer.

Example If an object that weighs 54 grams is weighed to be 53.2 grams, what is the percent error? Answer: 1.48 % If a car is thought to be going 32 mph but is actually clocked at 35 mph, what is the percent error? Answer: 8.57 %

“zero out” the scale to ensure that your weights are accurate. Zeroing A Scale “zero out” the scale to ensure that your weights are accurate.