Physics 101
February 21, 2017
Lecture 1
Introduction to Physics 101
Units and Dimensions (Ch. 1)
Announcements
• Attendance:
– Your attendance during the first two weeks of classes
is mandatory.
– In the event of an absence, your seat may be given to
a student on the wait list.
• Labs begin on Friday, February 24th.
– Purchase a lab manual at the bookstore before
coming to lab.
M. Afshar
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Units of Measurement
• We need units to
• We choose the
measure the following
International System
quantities:
(SI) of units:
– Length
– Meter ( )
– Time
– Second ( )
– Mass
– Kilogram (
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Units of Measurement (cont.)
• All quantities in mechanics can be measured in
terms of the three base units meters, seconds,
and kilograms.
• For example:
– The SI unit of force is the newton ( ):
– The SI unit of energy is the joule ( ):
– The SI unit of power is the watt ( ):
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Units of Measurement (cont.)
• All quantities in physics can be measured in
terms of seven base units:
– Meter ( ): Measures length or distance.
– Second ( ): Measures time or duration.
– Kilogram ( ): Measures mass.
– Kelvin ( ): Measures temperature.
– Ampere ( ): Measures electric current.
– Mole (
): Measures amount of substance.
– Candela ( ): Measures luminous intensity.
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Conversion of Units
• We often need
to convert
between SI and
non-SI units.
• Memorize the
conversions in
blue.
SI Units
Non-SI Units
1 meter (m)
= 100 centimeters (cm)
1 meter (m)
= 3.28 feet (ft)
1 meter (m)
= 39.37 inches (in)
1000 meters (m)
= 1 kilometer (km)
1609.34 meters (m)
= 1 mile (mi)
60 seconds (s)
= 1 minute (min)
3600 seconds (s)
= 1 hour (hr)
1 kilogram (kg)
= 1000 grams (g)
1 kilogram (kg)
= 35.27 ounces (oz)
1 kilogram (kg)
= 2.21 pounds (lb)
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Pay Attention to the Units
• Keeping track of the units can serve as a check on
your calculations. For example, which formula
for centripetal force is correct?
OR
• Analyze the units to find out:
,
Incorrect
Correct
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Practice Problem
The peregrine falcon – considered the
fastest animal – has a top recorded
speed of 242 miles per hour. What is
this speed in SI units?
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Practice Problem
A cylinder has base radius
and height
.
a) Calculate the volume of the cylinder in cubic
feet.
b) Convert the volume to SI units.
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