Question

What forces act on the cars of a roller coaster when they enters loops and turns after reaching the initial summit?

Answer 1

G FORCE

Answer 2

probably
1)gravity
2)normal contact force between car and track

Answer 3

In addition to what @Dikawar said, centripetal force would also be acting on the cars.

Answer 4

@Shane_B
Centripetal force in not a different force like gravity, friction, contact force. It is provided by these forces. In this case, vectorial sum of gravity and contact force will equal centripetal force.

Answer 5

Overthinking it...