6. A 3.0 kg box is resting on a horizontal surface and then a net force is applied to it. A graph of the net force acting on the box as a function of
time is shown to the right.
(a) What's the total impulse imparted to the box during the 12 s?
(b) What's the speed of the box at t = 5.0 s?
(c) What's the speed of the box at t = 12.0 s?

An alpha particle with kinetic energy 12.5 mev makes a collision with lead nucleus, but it is not "aimed" at the center of the lead nucleus, and has an initial nonzero angular momentum (with respect to the stationary lead nucleus) of magnitude l = p0 b, where p0 is the magnitude of the initial momentum of the alpha particle and b=1.40×10−12 m. (assume that the lead nucleus remains stationary and that it may be treated as a point charge. the atomic number of lead is 82. the alpha particle is a helium nucleus, with atomic number 2.) what is the distance of closest approach?