A balloon and a mass are fixed to a rod that can turn about the pivot at P. The balloon contains helium, which is less dense than air, so it exerts an upward force on the rod. The rod is horizontal and remains at rest. Which action makes the rod turn clockwise?
- AMove both the balloon and mass 10 cm to the left.
- BMove both the balloon and mass 10 cm to the right.
- CMove both the balloon and mass to the 25 cm mark.
- DMove the balloon to the 20 cm mark and the mass to the 30 cm mark.