1. Measurement
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What is a measurement?
A measurement is a number accompanied by a unit that defines the type of quantity being measured.
What does no naked numbers mean?
a number must always be accompanied by a unit to have meaning.
What’s the general rule in this physical science course?
no naked numbers
Any reported measurement must tell us three things:
1) units, which tell us what type of measurement was made. (e.g. meters, grams, and liters etc. was measured) 2) an order of magnitude (the size of the measurement which is read from your measuring device) 3) a statement about the uncertainty of the measurement
What is “uncertainty of measurement”?
it provides a statement concerning how closely (small a division) the measuring device can measure something.
What’s the measurement rule?
Determine the smallest division on the measuring device and then divide that number by 10. In general, the measurement will be written out to the number of decimal places obtained from dividing the smallest division by 10.
What does “accuracy of the measured values” mean?
Accuracy compares your measured value to some predicted value. The closer your experimental measurement is to that predicted amount the more accurate your measurement is considered. Accuracy is dependent on the measuring instrument you utilize and how well you use that instrument.
What do we calculate to inform us of accuracy?
percent error
What does “precision of those measured values” mean?
Precision is how consistent your measured values are.
When working with fluids notice that the top level of the fluid being measured in the cylinder is not a flat level surface. It is a concave surface called a
meniscus. All volume measurements are made using the bottom of the meniscus.
The density of an object can be obtained by
measuring the mass of the object and its volume. D= mass/volume
What are trials?
measurements are repeated several times
To obtain an average,
Add up all the measured values and divide by the number of trials performed.
In symbols, if the values involved are x1, x2, x3——–xn, (which means that there were a certain number of n trials performed, their average is computed by)
x1 + x2 + x3/ n
Scientific notation: 215= 2.15= 2.15 x 10^2 3.8625= 38625 x 10^-4
Because the original decimal point is at the end of the number, when it moves 2 to the left, the exponent is positive. Moving to the right, the exponent becomes negative.
1 gallon to cups
16 cups
1kg to pounds
2.2 pounds