In order to maintain straight and level unaccelerated flight...

In order to maintain straight and level, unaccelerated flight an aircraft has to generate how much thrust? a. Thrust equal the weight of the aircraft. b. Thrust greater than total drag at a given airspeed c. Thrust equal to the total drag at a given airspeed d. The same amount of thrust at all airspeeds

Transcript

00:01 Hi, here in this given problem, an airplane that is flying, making an angle theta with a horizontal.

00:11 At the constant speed, v0, angle theta, that is given to be equal to 25 degree.

00:18 Speed is constant, so that speed may be resolved into two components.

00:22 This is horizontal component.

00:24 We not cost theta vertically upward component.

00:28 We not sign theta, and we know.

00:32 Horizontal component of the velocity it gives the drag and vertical component of the velocity it gives the thrust okay so for the first part of the problem actually we have to find the statement which is not true so for the first one the thrust is greater in magnitude than the drag so as we know sign of an angle depends directly on the angle and cosine of the angle depends inversely on the angle.

01:09 So for 25 degree, sine theta will be less than cost theta.

01:19 Cost theta will be more as it depends inversely on angle theta.

01:23 So when angle is less, then cost theta will be more and sine theta will be less.

01:29 So we conclude thrust is less than the drag.

01:42 So here we conclude, but it is mentioned that thrust is greater in magnitude than the drag.

01:52 No, it is not true.

01:54 So a is not.

02:01 Now, the next one, the plane has a constant velocity.

02:05 Yes, of course, for b as the speed, speed is already mentioned that it is constant, constant speed.

02:14 And direction is also constant.

02:15 So as the speed and direction, both are constants...