00:01
For this problem, we're being given this equation for our distance of this aircraft, and we're being asked when it is airborne at 200 kilometers per hour, what is the time, right? so currently our units are in meters per second, so we need to convert that over.
00:15
But first we can find this speed, basically, right? so our speed is basically the derivative of this value here, so we find that dd equals 20 over 19, right? that's a speed in meters per second.
00:29
So you can say meters per second, right? and now that we have this, we can do a unit conversion.
00:36
If we look, let's move this actually over here.
00:40
So it'd be easier, 20 over 9 meters per second, right, times t because we can't forget the variable.
00:48
So if we convert this, we can first convert our meters, right, because we want kilometer meters.
00:54
A thousand meters is equal to one kilometer, right? because we're the meters and 60 seconds are in one minute and also 60 minutes are in one hour and then we can cross these values out right and this is basically equal to 20 times 60 times 60 right cam over 9 times 1 ,000 hours right and and then look at the zeros here, the zeros can cancel.
01:37
When we get that 72 over 9km over hour, t, basically is our speed function.
01:52
And then we can set this equal to the time it is airborne, which is 200 km per hour.
02:00
And our units cancel...