# Physics

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Rollercoaster has a dip that bottoms out in a vertical circle of radius r.

Passenger feels seat of car pushing upward on her with a force twice her weight as she goes through the dip.

If r = 20.0 m, how fast is rollercoaster going at bottom of the dip?

• Physics -

Potential energy at the topmost point = mg(2r)

Kinetic energy at dip bottommost point= 1/2 m (v^2)

so conservation of energy means

mg 2r = 1/2 m(v^2)

or 4rg= v^2
or v = 2sqrt(rg)
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