Question

A semicircular frame has two balls at the centre. The balls are free to move in the frame and no friction acts on it. Without moving the balls physically, how do you make both the balls positioned at the ends of the frame

• A. By tilting the frame through 180 degrees on either side rapidly
• B. By rotating the frame along an axis passing through the centre of the frame
• C. By tilting the frame through 45 degrees on either side rapidly
• D. None of these

Answer 1

The correct option is B By rotating the frame along an axis passing through the centre of the frame

By rotating the frame along an axis passing through the centre of the frame, the balls will experience a centrifugal force and hence will move away from the centre. Since they are constrained to move on the frame, they cannot move radially outwards, but will move along the frame. and hence after sometime, they will be positioned in opposite directions