The total force exerted on the 80,000-lb launch vehicle by the thrust of its engine, its w...

The total force exerted on the 80,000-lb launch vehicle by the thrust of its engine, its weight, and aerodynamic forces during the interval of time from t = 2 s to t = 4 s is given as a function of time by ΣF = (2000 = 400t2)i + (5200 + 440t)j + (800 + 60t2)k (lb). At t = 2 s, its velocity is v = 12i + 220j 30k (ft/s). What is its velocity at t = 4s?