The hammer-and-ruler trick
An unusual way to balance a hammer
Your attention, please! May we present to you a case of impossible – at first glance – equilibrium :)
- rubber bands;
Wrap two rubber bands around the handle of a hammer, forming a loop close to its head. Hook the loop around the end of a ruler and set the ruler on the brink of a horizontal surface. The hammer’s handle pushes upwards on one end of the ruler, while the hammer as a whole simultaneously pulls the ruler downwards. The system balances! You can also replace the ruler with another hammer – this will work too!
Since the hammer and ruler form a connected system, their joint movement is determined by the position of the center of mass of this system. As the hammer’s head is the heaviest element in the whole structure, we can assume, allowing for a slight inaccuracy, that the system’s center of mass is located there. Since its center of mass is located just below the fulcrum, the structure will balance. Moreover, this equilibrium is stable – if the system is forced to deviate from its position of equilibrium, it will rebalance itself. And if the construction is nudged, it will oscillate lightly.