00:01
All right, so let's say we have an airplane that has a mass of 18 ,700 kilograms, and it's flying at 690 kilometers per hour.
00:18
And we want to calculate the magnitude of the lift force on the plane.
00:22
So in this case, the lift force generated by the wings needs to be equal to the weight of the aircraft to hold it steady, to hold it level.
00:30
So our lift force is just going to be mg, and so 18 ,700 kilograms times 9 .8 meters per second squared.
00:45
This should come out to, we'll write as 1 .83 times 10 to the 5th newton's.
00:52
And then part b asks, now suppose that our plane, if i draw it from the front a little bit, is banked at a 42 .5 degree angle relative to the horizontal so maybe a little more extreme this is 42 .5 then what is the radius of the circle of the circle that the plane has to fly in given this assuming the lift force is the same and the speed is the same so our lift force is going to go in this direction the centripetal force we know goes towards the center of the circle so put it this way and so what we want is if our lift force is the same from problem one, and we draw an angle, this is probably not the best diagram if i'd redraw it with a straighter arrow.
01:42
This angle right here is going to be the same as our banking angle.
01:50
So you can see that the sign, the lift force times the sign of this angle should be equal to mv squared over r.
02:00
Or r is the radius of our circle.
02:02
And remember, our lift force was equal to mg.
02:04
We're told it doesn't change.
02:06
So it's equal to mg...