Minimum speed at the top of a loop
A roller-coaster car goes around a vertical loop of radius 10 m. Using g = 10 m/s², what is the minimum speed at the top for the car to stay on the track?
Answer B: explanation for every choice
A
This uses √(gr/2).
B
Correct. At minimum speed, gravity alone provides the centripetal force: mg = mv²/r, so v = √(gr) = 10 m/s.
C
This uses √(2gr).
D
This is gr, without taking the square root.
TakeawayTop of a loop at minimum speed: normal force = 0, so v = √(gr).
Equation usedCentripetal acceleration and force
Next question →Reviewed 2026-11-05 by a medical student. Spot an error? Report it with question ID cp111.