What two forces are combined to create the centripetal force on a cart on a roller coaster? 1-gravity and friction 2-friction and normal 3-normal and friction 4-normal and tension

The only forces acting on the rider are the upward normal force n exerted by the car and the downward force of gravity w, the rider's weight. These add together, as vectors, to provide the net force Fnet which is the centripetal force Fc, directed toward the center of the circle.

we need to know the time interval during which the force acts. impulse of force = momentum change

heats surface water up