Answer:
1 and 2
Step-by-step explanation:
It is given that, force exerted by air is negligible in any way.
Also, it is given that channel is in the shape of a segment of a circle with its center at O.
When it is within the frictionless channel at position 'Q',
A gravity exerts force on the ball in the downward direction. On the other hand, the channel pointing from Q to O also exerts a force on the ball.
However, there is no any force in the direction of motion. On the other hand, he channel pointing from O to Q does not exert a force on the ball.