Answer the following in brief:
Throughout history, many designs of perpetual machines (using wheels, weights or magnets) have been proposed but none actually work. Why do all real machines eventually slow down and stop? Explain in terms of work and energy.
Answer variants:
useful work
machines do not create energy
magnetism
machines increase the total amount of energy.
heat energy and sound energy
mechanical energy
wind energy
friction
only transform and transfer energy
Real machines eventually slow down and stop because some of the is continuously transformed into due to between moving parts. As a result, gradually decreases, and the machine cannot continue to operate without an external supply of energy. Therefore, perpetual motion machines are not possible because ; they , while some energy is always dissipated due to friction.