A) You can drop hammer and a feather, both will reach ground at the same time ( it was actually done in Apollo mission)
b) i. Yes, it is similar to weightlessness experienced by astronauts
ii. The phenomenon of "weightlessness" occurs when there is no force of support on your body. When your body is effectively in "free fall" in roller coaster, accelerating downward at the acceleration of gravity, then you are not being supported. Just like astronauts in space feel no force of support that we on earth feel due to gravity.
