posted by paul .
Scientists are experimenting with a kind of gun that may eventually be used to fire payloads directly into orbit. In one test, this gun accelerates a 7.0 kg projectile from rest to a speed of 4.0 x 103 m/s. The net force accelerating the projectile is 4.9 x 105 N. How much time is required for the projectile to come up to speed?
F = m*a
a = F/m = 4.9*10^5/7 = 7*10^4 m/s^2
t = (V-Vo)/a = (4000-0)/70,000=0.0571 s.