What part is attached to the bottom of the engine piston and spins when the piston moves?

The crankshaft is the correct answer because it is a crucial component in an engine that converts the linear motion of the pistons into rotational motion. As the piston moves up and down within the cylinder, the connecting rod, which connects the piston to the crankshaft, transfers that motion to the crankshaft. The crankshaft then spins, allowing the engine to produce power that eventually drives the vehicle's wheels.

The relationship between the piston and the crankshaft is fundamental in engines, as it enables the engine to function by allowing the energy created during combustion to be transformed into mechanical energy. Understanding this connection is vital for anyone involved in auto damage appraisal, as it highlights how different engine components work together to keep a vehicle operational.