Chapter 1: Introduction
Glossary
1.1 What is Biomechanics
biomechanics
the application of principles of mechanics to the study of living systems
mechanics
the branch of science concerned with the interaction between forces and objects
1.2 Physical Quantities and Units
- physical quantity
- characteristic or property of an object that can be measured or calculated from other measurements
- SI units
- the international system of units that scientists in most countries have agreed to use; includes units such as meters, liters, and grams
- base quantity
- physical quantity chosen by convention and practical considerations such that all other physical quantities can be expressed as algebraic combinations of them
- base unit
- standard for expressing the measurement of a base quantity within a particular system of units; defined by a particular procedure used to measure the corresponding base quantity
- derived quantity
- physical quantity defined using algebraic combinations of base quantities
- derived units
- units that can be calculated using algebraic combinations of the fundamental units
- English units
- system of measurement used in the United States; includes units of measure such as feet, gallons, and pounds
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- kilogram
- SI unit for mass, abbreviated kg
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- meter
- SI unit for length, abbreviated m
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- metric system
- system in which values can be calculated in factors of 10
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- second
- the SI unit for time, abbreviated s
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- units
- standards used for expressing and comparing measurements
1.3 Accuracy and Precision
- accuracy
- the degree to which a measured value agrees with an accepted reference value for that measurement
range
the difference between the lowest and the highest measured values
- discrepancy
- the difference between the measured value and a given standard or expected value
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- method of adding percents
- the percent uncertainty in a quantity calculated by multiplication or division is the sum of the percent uncertainties in the items used to make the calculation.
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- percent uncertainty
- the ratio of the uncertainty of a measurement to the measured value, expressed as a percentage
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- precision
- the degree to which repeated measurements agree with each other
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- significant figures
- used to express the precision of a measuring tool used to measure a value
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- uncertainty
- a quantitative measure of how much measured values deviate from one another
average (arithmetic mean)
The sum of all the measures divided by the number of measurements
mean absolute difference
The absolute value of the uncertainties for each measure, and then reporting the average of those
variance
The average of the squares of the difference from the mean.
standard deviation
The square root of the variance
1.4 Conversions
- conversion factor
- a ratio that expresses how many of one unit are equal to another unit