An aircraft has a net excess thrust of 14,000 lbs and weighs 36,000 lbs. if it starts from 30 kts, what is its velocity (in knots) after 15 seconds?

"(witch the answer is 141.218) you need this for the net part"

how many feet down the runway would the aircraft in problem 4 be at rotation if vr = 160 kts? (the aircraft is at 135 feet down the runway when it starts its takeoff and starts from 30kts)