HOW ACTION - REACTION FORCE PAIRS WORK

WALKING

You push on the ground with an action force - planet Earth pushes back on you with a reaction force that is equal in strength and opposite in direction. Your body is much easier to move than Earth, so you move because our super massive, immovable planet is pushing you forward! Yes, in order to walk to the North, your legs and feet have to push to the South!

DRIVING

Your school bus pushes on the road with an action force – the road (planet Earth) pushes back on your school bus with a reaction force that is equal in strength and opposite in direction. Your bus is easier to move than the road (Earth) so your bus moves forward because our super massive, immovable planet is pushing back on it!

SWIMMING

A whale pushes on the ocean with its powerful tail (action force) – the ocean water pushes back on the whale with a reaction force that is equal in strength and opposite in direction. The whale is easier to move than the ocean, so the whale moves forward because the super massive ocean water is pushing it forward!

ROWING/PADDLING

The oars of your row boat push on the lake water (action force) – the lake water pushes back on the oars/rowboat with a reaction force that is equal in strength and opposite in direction. The boat is easier to move than the lake, so the boat moves forward because the lake is pushing it forward! Yes, to move a row boat across a lake toward the setting Sun (west), your oars have to push toward the East!

FLYING

A bird pushes on the atmosphere with its wings (action force) – the air pushes back on the bird with a reaction force that is equal in strength and opposite in direction. The bird is easier to move than the atmosphere, so the bird moves forward because the air is pushing back on it!

There are some instances where action forces (and subsequent reaction forces) cannot be exerted. We’ll look at these interesting examples in the next post