1. The problem statement, all variables and given/known data A 0.20-kilogram mass is sliding on a horizontal, frictionless air track with a speed of 3.0 meters per second when it instantaneously hits and sticks to a 1.3-kilogram mass initially at rest on the track. The 1.3-kilogram mass is connected to one end of a massless spring, which has a spring constant of 100 newtons per meter. The other end of the spring is fixed. 2. Relevant equations F = -kx KE = 1/2m(v)squared momentum = mass x velocity 3. The attempt at a solution The first couple parts of the problem ask you to solve for the linear momentum and kinetic energy of the masses before and immediately after collision. I interpreted "immediately after the impact" to indicate that I'm supposed to calculate the linear momentum/KE of the masses without taking the spring into account. a. momentum before impact = 0.6 kg m/s KE before impact = 0.9 Joules b. momentum after impact = 0.6 kg m/s KE after impact = 0.3 J c. Determine the amplitude of the harmonic motion. d. Determine the period of the harmonic motion. I don't really know where to start on parts C and D- I thought to use F=mA to determine the spring force (F=-kX) needed to stop the motion of the mass since the k value is provided (100 n/m), but there's no A value to plug into F=mA. I suspect that KE initial + PE initial = KE final + PE final might factor in because at maximum amplitude PE = 0.3 J, but I don't know where. How might I solve this? EDIT: Took another crack at it; am I on the right track? PE final = 0.3 Joules PE = (1/2)k(x)squared 0.3 J= (1/2)*(100 N/m)*x squared x = .0015 m Would that be the amplitude? If so, how might I find the period? EDIT 2: Went Wikipedia hunting and came up with the formula T = 2pi ROOT(m/k). Plugged in all the numbers and came out with .76 seconds. I haven't a clue if that formula applies for a mass on an air track as it applies for a hanging mass, though, so please tell me whether I've got it right or all wrong. In case you're curious, this problem is from the 1995 Physics AP free response section.