Interesting centre of gravity problem

Question

Tom has cut the right end of a uniform shaft of 40 cm in length. How much and to which direction the center of gravity of the remaining shaft moved? The answer is 20 cm to the left.

Answer 1

Solution:

This problem requires little imagination, and here is the solution:

Assume The original shaft length is L. The center of gravity originally was L/2 from the left, as you cut 40 cm from end, the shaft length is reduced by 40 cm, assume the final shaft length is L' = L - 40. In that case the center of gravity for the shaft would be L'/2 = ( L-40/2) = L/2 -20.

comparing the location of the center of gravity before and after the cut

Before = L/2 to the left

After = L/2 - 20 to the left and therefore the center of gravity moves 20 cm to the left