IMPOSSIBLE Physics homework problems. Does anyone know how to solve these monsters?

[edvard_munch]

1. Find the acceleration of the masses shown in Figure 6-32, given that m1 = 1.2 kg, m2 = 2.0 kg, and m3 = 3.5 kg. Assume the table is frictionless and the masses move freely. ___m/s2
http://www.webassign.net/walker/06-27alt.gif

2. Find the linear speed that the bottom of a test tube must have in a centrifuge if the centripetal acceleration there is to be 52810 times the acceleration of gravity. The distance from the axis of rotation to the bottom of the test tube is 6.9 cm. ___km/s

3. Driving in your car with a constant speed of 12 m/s, you encounter a bump in the road that has a circular cross section, as indicated in Figure 6-35. If the radius of curvature of the bump is r = 31 m, find the apparent weight of a 70 kg person in your car as you pass over the top of the bump.___N
http://www.webassign.net/walker/06-30alt.gif

Thanks and Prosperity to anyone who offers some viable help.