‫Welcome back.
‫So imagine that we have a drone and that drone has four propellers, four motors, and they rotate very,
‫very fast.
‫So you have your M1 and M3 that rotate counterclockwise and then you have M2 and M4 that rotate clockwise.
‫And here's the propeller itself with two blades.
‫Let's just assume that this propeller is motor one and we will also attach a separate body frame to
‫it.
‫You will have X and one.
‫Why stop and one and finally, the Z sub M one as well, and this propeller rotates about its body frame,
‫the axis Z sub and one.
‫And it rotates at omega one radians per second, so counterclockwise.
‫Now, this propeller also has mass moments of inertia about its three axis.
‫However, since we only rotate about its body from Z axis, then we only need to care about the mass
‫movement of inertia, about this Z sub and one.
‫And we call it J, sub T, P, sub M one, and the units are again KG's times meters squared.
‫So this is the mass moment of inertia about the propeller's body frame, Z axis.
‫And then, of course, you have a mass movement of inertia for your motor to model three and more four.
‫However, we're going to assume that they are all equal for all propellers.
‫So we're going to omit these subindices here and we're just going to say that the propellers mass movement
‫of inertia about its body from Z axis, about the propellers body frames, the axis is just Jessopp
‫TPE.
‫So if you look at the drone now, then you see that the rotation of the propeller, M1 and M3, they
‫produce angular momentum like this.
‫This is four and one, and this is four and three, so the angular momentum for M one equals.
‫Jessup, t.P, Times, Elnaggar, one, and the angular momentum for more three equals Jessopp t.P times
‫Omega three like this.
‫And it makes sense that this is the direction, right?
‫It's all happening according to your right hand rule.
‫So if you take your right hand and then you curl your fingers in the direction of the rotation like
‫this, then your thumb will point up.
‫However, in case of M2 and for you are rotating clockwise.
‫So what do you think?
‫In which direction would you have your angular momentum up or down?
‫Try to do it as an exercise, so just write down the equations for the angular momentum for M2 and M4
‫and the direction, and then you'll see it in the next video.
‫Thank you very much.
‫And see you there.