Caption: Playground merry-go-round with children: playful, happy, carefree---little know they of F=ma.
Playground merry-go-rounds have become a bit uncommon since they are considered a bit too dangerous.
Playground merry-go-rounds are non-inertial frames because they are rotating which means they are accelerating.
There are accelerations without forces.
Throw a ball on a rotating playground merry-go-round and it follows a curved path in the horizontal plane even though there is no force to bend its path.
From the ground frame which is an inertial frame (to sufficient approximation), the ball's path is straight.
Credit/Permission: ©
User:Jayhawksean,
2005 /
Creative Commons
CC BY-SA 3.0.
Image link: Wikipedia:
File:Merry-go-round.jpg.
Local file: local link: merry_go_round.html.
File: Mechanics file:
merry_go_round.html.