My issue/knowledge Hello all, I think this is my first time posting a question here (I have read the guidelines). This problem is not in my text book or notes, and I'm not sure how to go about it. Online all I can find about air drag equations requires knowing variables which I'm not given here, so I'm having a great deal of difficulty (for 6 hrs+ now). I'm sorry if my attempts look weak too you, I have really tried. Thanks. 1. The problem statement, all variables and given/known data "A 1500kg car accelerates in first gear to from 0 to 55km/h in 2.7 seconds. In fifth gear from 150 km/h to 220 km/h in 23 seconds. Assume the drag force is negligible at low speeds but increases as the square of the velocity. Estimate the drag force of friction at a speed of ~200 km/h" 2. Relevant equations v^2? F=m*a a=F/m a=v/t fk=ukmg uk= a/g 3. The attempt at a solution a=v/t (55km/h-0km/h) / 2.7 seconds= 5.658 m/s^2 (converted to metric) (220km/h-150km/h) / 23 seconds= 0.845 m/s^2 m*a 1500kg*5.658m/s^2= 8487N 1500kg*0.845 m/s^2= 1267.5N So I get here and have no idea how to proceed. What I feel like maybe I should do is imagine it like a normal friction problem and just find acceleration it takes to 200km/h, divide by gravity, uk=a/g. Then again I'm thinking that square of velocity is really important, so maybe subtract force of car it takes to get to 200km/h from 200km/h^2, then divide by mass to get acceleration, divide that by gravity? I feel like I'm talking nonesense now.