i have nooooooo idea how to convert anything.. physics help?

Question

an airplane travels 1200 km at a speed of 1000 km/h. it then encounters a headwind that slows it to a 950 km/h for the next 1800 km. what is tge average speed in m/x for this trip?

thats an example... how do you convert.. what are all the conversions... like how many miles are in km ect all common ones please

Answer 1

Because all of the distance units are in km and the speed units are in km/h, the units are all consistent with each other and you have the option of waiting until the end of the problem to convert the average speed to m/s (meters/second). Miles and other nonmetric distance units are irrelevant; they don't enter the problem at all.

I won't do the problem itself for you, but let us say that v is your final answer in km/h. There are 1000 meters (m) in 1 kilometer (km), 60 seconds (s or sec) in a minute (min) and 60 minutes in an hour.

When converting units in proportions like this, the idea is to get all the units to cancel except those that appear in the final answer. That is, v km/h * 1000 m/1 km has units of km in the numerator and denominator that cancel just as common factors in a numeric fraction would. This would leave the result as 1000v m/h.

Similarly, you can cancel the hour units of time in the denominator of your speed units:
1000v m/h * 1 h/60 min * 1 min/60 sec
= 1000/3600 * v m/s
= 1/3.6 v m/s. Notice that the hours and minutes time units cancel, leaving seconds in the denominator.

Also notice that you now have an overall conversion factor from km/h to m/s that you can use anytime. If you prefer to convert your speeds to m/s before working the problem, you can do so - just divide each speed in your problem by 3.6 to get the speed in m/s. If you do that, you should also convert all of your distance units to meters by multiplying your distances by the factor 1000 m / 1 km to make your distance units compatible with your speed units.

You could still get the correct answer to this particular problem without converting the distances, but the corresponding units for any time measurements would be in kiloseconds, a strange unit of time for such a problem. Operating in strange hybrid systems of units, e.g., distances in km, speeds in m/sec, and times in ksec is possible but nonstandard and error-prone.

Answer 2

To convert units you always multiply by one. The trick is to pick your "one" in such a way that it cancels the unit you want to get rid of and introduces the unit you want.

For example, there are 1000 meters in a kilometer. You could express this as "one" in two ways:

1000 meters / 1 kilometer

1 kilometer / 1000 meters

The first is used if you want to convert kilometers to meters. The second is used if you want to convert meters to kilometers.

Another pair you'll need for this problem are

3600 seconds / 1 hour
1 hour / 3600 seconds

HTH...

Answer 3

You can find all conversions in physics books like Holliday and resnik et al. But how to use them:
They have a table for time conversions, speeds conversions, length and all that. For example it says 1 mile = 1609.3 m , then you say:
1 mile = 1609.3 m
x mile = 1 m
==> x=(1*1)/1609.3=0.0006213711922373339
so 1m=0.0006213711922373339 mile

The same for every thing. If it is mixed units for example velocity is given by miles/sec and you want to change it to meters/second just say
1 mile = 1609.3 m
so 1 mile/sec=1609.3 m / sec
for example what is 85 mile/sec in meters per second?
it is (85*1609.3 m)/s=136790.5 m/s !
Now what is 85 mile/sec in meters per HOUR?
ok!
it is (85*1609.3 m)/(1/3600 Hour)=136790.5*3600 m/hour=492445800 m/hour=492445.8 km/hour
:)

Answer 4

sorry im bad at metric too T_T