Tag Archives: Moment of Inertia

A2L Item 107

Goal: Reason with the concept of moment of inertia

Source: UMPERG-ctqpe116

The rotational inertia of the dumbbell (see figure) about axis A is
twice the rotational inertia about axis B. The unknown mass is

  1. 2 kg
  2. 4 kg
  3. 5 kg
  4. 7 kg
  5. 10 kg
  6. None of the above
  7. Cannot be determined

Commentary:

Answer

(4) Students can get bogged down in calculations when it is unnecessary
to do detailed calculations. Proportional distances to the axes is all
that is needed. This problem presents a good opportunity to discuss
problem solving procedures.