wheel and axle
a special one dude!
A pulley isn't a kind of simple machine, it is a simple machine
They were the first kind of roller skates to be invented, and were later repurposed as Rollerblades.
A train is not a simple machine.
The compound noun roller-skate is a common noun, a word for any roller-skate of any kind, anywhere.A proper noun is the name of a specific person, place, or thing; for example:Harborena Roller Skating Rink Inc., Hoquiam, WashingtonLenexa Supreme Roller SkatesNational Museum of Roller Skating, Lincoln, Nebraska
IT's NOT A SIMPLE MACHINE!
its not a simple machine
It is a simple lever.
Rope is not a simple machine on its own, it's a simple machine on a wheel and axle, then it's a pulley.
a compound machine is a combination of simple machines
lever
lever