EXTREMELY HARD Physics homework problems with seemingly no correct answers?!?

[edvard_munch]

I'm stumped. Any help would be greatly appreciated.

1. 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. The radius of curvature of the bump is 36.7 m. At what speed must you go over the bump if people in your car are to feel "weightless"? ___m/s
http://www.webassign.net/walker/06-30alt...

2. A skateboard accident leaves your leg in a cast and supported by a traction device, as in Figure 6-27, with = 29.5°. Find the mass m that must be attached to the rope if the net force exerted by the small pulley on the foot is to have a magnitude of 36 N._____kg
http://www.webassign.net/walker/06-22alt...

3. A 0.075 kg toy airplane is tied to the ceiling with a string. When the airplane's motor is started, it moves with a constant speed of 1.25 m/s in a horizontal circle of radius 0.37 m, as illustrated in Figure 6-40.
Additional Details


#3 (Edited)

A 0.075 kg toy airplane is tied to the ceiling with a string. When the airplane's motor is started, it moves with a constant speed of 1.25 m/s in a horizontal circle of radius 0.37 m, as illustrated in Figure 6-40. Find the angle the string makes with the vertical and the tension in the string.

___°
___N

http://www.webassign.net/walker/06-34.gi...

AND the answers (1) 62 m/s
2) 55 kg
3) 35 degrees and 4.2 N

are NOT correct. Does anyone out there know how to CORRECTLY explain and solve these physics problems?