Friction always slows things down (like wheels rubbing the ground).

Air resistance pushes back on moving things (like wind).

Energy is always lost as heat or sound.

No machine is perfect — parts wear out or break.

You always need to add energy to keep something moving.

Gravity pulls things down and changes their motion.

Magnets and motors still lose energy over time.

It breaks the laws of physics, like the law of energy.

Scientists have never made one that truly works.

Even in space, there’s tiny resistance that slows things.