Here's the question.(adsbygoogle = window.adsbygoogle || []).push({});

A roller coaster at an amusement park has a dip that bottoms out in a vertical circle of radius r. A passenger feels the seat of the car pushing upward on her with a force equal to twice her weight as she goes through the dip. If r=20.0 m, how fast is the roller coaster traveling at the bottom of the dip?

I'm having some real troubles answering this problem. Thus far, here's

what I've come up with.

Fc = ( mv^2 ) / r

FN - 2mg = ( mv^2 ) / r

2mg - mg = ( mv^2 ) / r

(2mg - mg )(r) = ( mv^2 )

(2mg - mg )(r) = ( v^2 )

sqrt( (2mg - mg )(r) ) = v

sqrt( ( 19.6 - 9.8 m/s^2 )( 20.0m ) ) = v

14 m/s = v

I've been informed that 14 m/s is not the correct answer and that to one digit the correct answer is 10 m/s.

It seems to me that I have all the right pieces, but I may be missing something. Will someone help, please? Big thanks!

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Virtical Circles

**Physics Forums | Science Articles, Homework Help, Discussion**