30 to 45 minutes on Lift and Drag??? Doing justice to that would take a couple of days. My advice is keep it simple and don't try to cram too much in. Give a preamble saying that you're only going to cover certain aspects and the rest will be covered in a (non-existant) later lecture. Structure the lecture to give an intro - what you're going to say and why; the main body; a conclusion saying what you've said and asking questions to consolidate and ensure that your audience has understood what you said.