Post on 14-Jan-2016
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Unit Conversions
Are Units important?
3
Are Units important?
Project Cost
$327.6 million total for both orbiter and lander.
•$193.1 million for spacecraft development,
•$91.7 million for launch
•$42.8 million for mission operations.
http://mars.jpl.nasa.gov/msp98/orbiter/ 4
Are Units important?
"The 'root cause' of the loss of the spacecraft was the failed translation of English units into metric units in a segment of ground-based, navigation-related mission software, as NASA has previously announced," said Arthur Stephenson, chairman of the Mars Climate Orbiter Mission Failure Investigation Board."
http://mars.jpl.nasa.gov/msp98/orbiter/ 4
ConvertingInches to centimeters
Convert 10.0 inches to centimeters
ConvertingInches to centimeters
10.0 in
We start by writing down the number and the unit as a FRACTION
1
ConvertingInches to centimeters
10.0 in
1 in
2.54 cm
Our conversion factor for this is 1 in = 2.54 cm.Since we want to convert to cm, it goes on the top.
1x
ConvertingInches to centimeters
10.0 in
1 in
2.54 cm
Now we cancel and collect units. The inches cancel out, leaving us with cm –
the unit we are converting to.
1x
ConvertingInches to centimeters
10.0 in
1 in
2.54 cm = 25.4 cm
Since the unit is correct, all that is left todo is the arithmetic...
The Answer
1x
Even though we have two different numbersand two different units, they represent theexact same length. You can check this by looking at a ruler – find the 10 in mark anddirectly across at the cm side. What numberdo you find?
A more complex conversionkm to mhr s
In order to work a NSCI 110 homework problem, we need to convert kilometers per hour into meters per second. We can do both conversions at once using the same method as in the previous conversion.
80 km
1 hr
A more complex conversionkm to mhr s
Step 1 –Write down the number and theUnit as Fraction!
80 km
hr
1 hr
3600 s
A more complex conversionkm to mhr s
First we’ll convert time. Our conversion factor is1 hour = 3600 sec. Since we want hours to cancel out, we put it on the top.
1x
80 km
hr
1 hr
3600 s
1000 m
1 km
A more complex conversionkm to mhr s
Next we convert our distance from kilometers to meters. The conversion factor is 1 km = 1000 m.Since we want to get rid of km, this time it goes on the bottom.
1x x
80 km
hr
1 hr
3600 s
1000 m
1 km=
A more complex conversionkm to mhr s
Now comes the important step – cancel and collect units.If you have chosen the correct conversion factors, you should only be left with the units you want to convert to.
ms1
x x
80 km
hr
1 hr
3600 s
1000 m
1 km=
80,000 m
3600 s
A more complex conversionkm to mhr s
Since the unit is correct, wecan now do the math – simplymultiply all the numbers on thetop and bottom, then divide thetwo.
1x x
80 km
hr
1 hr
3600 s
1000 m
1 km=
80,000 m
3600 s=22.2 m
s
A more complex conversionkm to mhr s
The Answer!!
1x x
80 km/hr and 22.2 m/s are both velocities. A car that is
moving at a velocity of 80 km/hr is traveling the
exact same velocity as a car traveling at 22.2 m/s.
Convert a rate from one unit to another with a change in both units
Convert a rate from one unit to another with a change in both units