Physics
posted by Nikita .
A roller coaster ride includes a circular loop with radius R = 13.3 m. What minimum speed must the car have at the top to stay in contact with the tracks?

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Basically, the centripetal acceleration has to offset gravity, 9.8 m/s².
Since the centripetal acceleration is given by v²/r, so we equate the two quantities to get
v²/r = 9.8
v=sqrt(9.8*r) m/s
= sqrt(9.8*13.3) m/s
= 11.4 m/s.