Answer:
A homopolar motor is a direct current electric motor with two magnetic poles, the conductors of which always cut unidirectional lines of magnetic flux by rotating a conductor around a fixed axis so that the conductor is at right angles to a static magnetic field.
Explanation:
knives, axe ,blades and nails are examples of potential energy
or sharp objects
I would say 150 joules, i don't know if its right though check