32
Summary
Selected Vocabulary
matter...............................Anything that is affected by gravity.
light...................................Anything that can travel from one place to another through empty space
and can influence matter, but is not affected by gravity.
operational definition........A definition that states what operations should be carried out to measure
the thing being defined.
Système International........A fancy name for the metric system.
mks system........................The use of metric units based on the meter, kilogram, and second. Ex-
ample: meters per second is the mks unit of speed, not cm/s or km/hr.
mass..................................A numerical measure of how difficult it is to change an object’s motion.
significant figures..............Digits that contribute to the accuracy of a measurement.
Notation
m......................................symbol for mass, or the meter, the metric distance unit
kg......................................kilogram, the metric unit of mass
s........................................second, the metric unit of time
M-.....................................the metric prefix mega-, 10
6
k-......................................the metric prefix kilo-, 10
3
m-.....................................the metric prefix milli-, 10
-3
µ
-......................................the metric prefix micro-, 10
-6
n-......................................the metric prefix nano-, 10
-9
Summary
Physics is the use of the scientific method to study the behavior of light and matter. The scientific method
requires a cycle of theory and experiment, theories with both predictive and explanatory value, and
reproducible experiments.
The metric system is a simple, consistent framework for measurement built out of the meter, the kilogram,
and the second plus a set of prefixes denoting powers of ten. The most systematic method for doing
conversions is shown in the following example:
370ms
×
10
–
3
s
1ms
=0.37s
Mass is a measure of the amount of a substance. Mass can be defined gravitationally, by comparing an
object to a standard mass on a double-pan balance, or in terms of inertia, by comparing the effect of a force
on an object to the effect of the same force on a standard mass. The two definitions are found experimentally
to be proportional to each other to a high degree of precision, so we usually refer simply to “mass,” without
bothering to specify which type.
A force is that which can change the motion of an object. The metric unit of force is the Newton, defined as
the force required to accelerate a standard 1-kg mass from rest to a speed of 1 m/s in 1 s.
Scientific notation means, for example, writing 3.2x10
5
rather than 320000.
Writing numbers with the correct number of significant figures correctly communicates how accurate they
are. As a rule of thumb, the final result of a calculation is no more accurate than, and should have no more
significant figures than, the least accurate piece of data.
Chapter 0Introduction and Review