I’m attempting to write an aircraft simulation game with believable physics, although it doesn’t have to be precise but I’m having a bit of trouble getting it off the ground so to speak. When I plug numbers into the drag and rolling resistance formulas, I don’t think I get accurate results, so I must be doing something wrong along the way, as I’m by no means an expert at maths or physics. I’m not looking at lift just yet, but obviously I will at some point. I’m sure I’m making plenty of silly mistakes, so please correct me where I go wrong. I’ve been attempting to get my head around this for a couple of days but I don’t seem to be making much progress. For example, let’s take a Tornado GR4 with the following specs: (http://www.fas.org/man/dod-101/sys/ac/row/tornado.htm) Weight: 13890kg Thrust: 38.7kN Wing area: 26.6m^2 Am I right in thinking I should be looking at rolling resistance rather than static friction in order to get the object (aircraft) moving along the ground? Rolling resistance: F = C * Nf Where F is the rolling resistance force C is the rolling resistance coefficient Nf is the normal force Let’s take C to be 0.01 (ordinary car tyres on concrete). Would the mass of the object be 13890 kg or 13890 / 9.81 = 1415.9 kg? I’m a bit confused because force in Newtons has the units of kg ms^-2 but mass has the units of kg, although the units given for the weight (force), is in kg? If I were to take 1415.90 kg to be the mass, the normal force (Nf) would be 13890 N (1415.9 * 9.81)? I’m not sure that sounds right though :/ So the force required to get the object moving would have to be greater than 0.01 * 13890 = 138.9N? For drag: D = Cd * A * 0.5 * r * V^2 Where D is the drag Cd is the drag coefficient. Say 0.02 A is the reference area (for an aircraft, it’s the wing viewed from above which makes it easier/comparable to calculate the lift?). 26.6 m^2 r is the density of the air. 1.225 kg m^-3 (at sea level) V is the velocity. Say 44 m^s-1 D = 0.02 * 26.6 * 0.5 * 1.225 * 44^2 = 630.8456 N So how would I then calculate how much to slow the object down by? This is quite challenging for me as you can probably tell, but I hope to eventually grasp it. I’d appreciate any help that anyone is able to offer :) Many thanks.