Question

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 9.7-kg projectile from rest to a speed of 6.5 × 103 m/s. The net force accelerating the projectile is 8.0 × 105 N. How much time is required for the projectile to come up to speed?

Answer 1

F = m*a
a = F/m = 80000/9.7 = 8247 m/s^2
V = Vo + a*t
t = (V-Vo)/a = (6500-0)/ 8247 = 0.788 s.

Answer 2

At an instant when a soccer ball is in contact with the foot of the player kicking it, the horizontal or x component of the ball's acceleration is 750 m/s2 and the vertical or y component of its acceleration is 990 m/s2. The ball's mass is 0.38 kg. What is the magnitude of the net force acting on the soccer ball at this instant?