Deepak Patra
Last Activity: 10 Years ago
The correct option is: (C) the upward-moving marble has ay > -9.8 m / s2.
Imagine that the marbles are shot by the pipe such that they move with constant velocities. This would ensure that the distance between both the marbles and the pipe remains the same with time and rule out the option (B).
Therefore, the distance between the marbles and the pipe increases only when the velocity of the marbles relative to the velocity of the pipe increases over time. Thus, a marble moving upward must have a positive acceleration with respect to the pipe. If the pipe falls vertically with acceleration -9.8 m /s2 , the marble moving upward should have acceleration greater than -9.8 m /s2 such that the acceleration remains positive relative to the pipe.
Therefore, (C) is the correct option.