Abox weighing 40.0 n, is initially at rest on a rough 6.0 m long ramp. the ramp is inclined at 30.0° with the horizontal. as the box slides down the ramp it experiences a frictional force of 6.0 n against its motion. determine the velocity of the box when it reaches the bottom of the ramp.

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?