Just because you hit the stop button on a piece of equipment, doesnt necessarily stop all the parts. Here is an example courtesy of the British Columbia Workers Compensation Board:
A hewsaw operator had his right forearm medically amputated after suffering severe cuts and fractures. A jammed log had stalled the drive motor and automatically shut off power to the saw. Unfortunately, the braking system of this saw does not work during power outages or when the drive motor stalls. The operator removed a portion of the guarding system where he could see only the one cutting head that had stopped because of the jammed log. There was no sensor to indicate if all cutting heads had come to a complete stop. When the worker reached in to remove the jammed log, his right hand was caught in one of the cutting heads that was still rotating and coasting to a stop.
High speed rotating parts and motors dont stop just because the machine is stopped. Many tools and equipment parts continue to coast when power is cut.
Today, look at where you work. Are there high speed rotating parts? Think twice before reaching anywhere near them and ensure that all parts are truly not moving.