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Chapter 1
Measurement
In this chapter we will explore the following concepts:
1. Measurement of a physical parameter
2. Units, Systems of units
3. Basic Units in Mechanics
4. Changing units
5. Significant figures
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View Full Document In Physics we carry out experiments in which we measure physical
parameters. We then try to deduce the relationship between the measured
quantities.
We usually express this relationship in the form of a mathematical
equation which we call the “
physical law
” that describes the phenomenon
under study.
A familiar example is Ohm’s law.
The experiment in this case
consists of measuring the electric voltage difference
V
applied across a
conductor and the resulting
electric current
I
that flows through the
conductor
If we plot
I
versus
V
we get a straight line.
This is expressed in the form:
The equation is known as: “
Ohm’s Law
”
R
is known as the “resistance” of the conductor
Constant
V
R
I
=
=
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Assume that you step on your bathroom scale and that it reads 120
The number alone is meaningless.
It must be accompanied by the units
120 lb is a very different reading from 120 kg!
Conclusion:
For every physical parameter we will need the appropriate units
i.e. a standard by which we carry out the measurement by comparison to the
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This note was uploaded on 09/24/2008 for the course PHY 107 taught by Professor Han during the Spring '08 term at SUNY Buffalo.
 Spring '08
 HAN
 mechanics

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