In Example 10.10 (Section 10.6) the rotational kinetic energy of the professor and dumbbells increases. But since there are no external torques, no work is being done to change the rotational kinetic energy. Then, by Eq. (10.22), the kinetic energy must remain the same! Explain what is wrong with this reasoning, which leads to an apparent contradiction. Where does the extra kinetic energy come from?

Eq.(10.22)

Transcribed Image Text:

Final rotational kinetic energy Total work done on-- a rotating rigid body lw,dw, ="}lw} - }lw?, lof (10.22) = work done by the net external torque Initial rotational kinetic energy