Question

Please explain how to get answer: at what speed must a rollercoaster be traveling when upside down at the top of a loop, with a radius of 8.6 meters, if the passengers not wearing seat belts don't fall out

Answer 1

assume that centripetal acceleration is equal to acceleration due to gravity
you can apply this formula: \(\sf a_c=\frac{v^2}{r}\) evaluate and solve for V:
\(\sf v=\sqrt{a_cr}\) plug in your values and you'll get it

Answer 2

centripetal force IS equals to acceleration due to gravity { we can't assume here can we @Jadzia :) , we are risking passenger's lives here !!! :D }