Name: ______________________
Introductory Exercise 05: More unit conversions
Allotted time: 45 minutes in-class
Practice 1) (This one is worth 3 pts)
Let’s practice converting between “km” and “mile” again as you have done in previous
exercise, but here we will go the other way from km to mile. Convert 1 km following
this order, km  m, m  cm, cm  inch, inch  feet, feet  mile, show all conversion
steps, conversion factors and round off to 4 decimal places.
Practice 2) An “Astronomical Unit”, or AU, is defined as the average distance between
the Sun and Earth which is roughly 150 million kilometers (149.60 x 10 6 km). Simply
use the result from the above practice to convert to mile (one convert factor, one step).
Express or re-express your answer in proper prefix or power.
(Read more about AU in Wikipedia: http://en.wikipedia.org/wiki/Astronomical_unit)
Practice 3) Convert 1 mph to m/s. Note that “mph”, or miles per hour, is a combinedunit with “mile” and “hour”, thus the overall conversion shall be done in two separate
conversions by 1) first focus on “mile” and convert to “meter” and then 2) turn attention
to “hour” and convert to second. Do not let the complex expression confuse you, and
simply focus on one conversion at a time.
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Name: ______________________
What is the corresponding speed of 100 m/s in mph? (Reverse the steps of the previous
practice and go from m/s to mph by going through the conversion factors “in inverse”
and “backward”)
Perhaps one of the most common yet important simple conversions is simply converting
within the Metric system in which you go from one particular prefix to another.
Practice 5) Convert 100 kg to gram. For this you need to go back to review the
conversion between kg and g and the meaning of the prefix “k”, and write out a
conversion factor. Do not just use your “intelligence” and write out a single number, but
show the conversion factor and work out the conversion as demonstrated in all examples.
Practice 4) Astronomy as an observational science works with visible lights that has very
tiny and short wavelength. Write out the wavelength of red-light which is 700 nm
(nano-meter) in meter and in micron (micro-meter).
a) To convert to meter, again you need to know the relationship between “nm” and
“m”, and the right conversion factor to use. Again avoid being too intelligent by
taking short cuts and practice the formal procedure.
b) To go from nm to micron, the most clear and systematic approach is to connect to
the fundamental unit, which is “m”, and avoid being too cutesy with converting nm
to micron directly. Think what is the conversion factor for “nm to m” and then
from “m to micron”. This should be easier now because you have already looked
into “prefixes” in the Metric system. So connect nm to m first by dealing with the
prefix n, and then from m to micron by knowing how “micro”-meter relates to
meter.
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