Rowing, swimming, walking
To go forwards, something must be pushed backwards. That is the practical meaning of the third law.
Rowing a boat
What rowing a boat does is push the water backwards with the oar. That is, the force is applied by the oar to the water — that is the action.
The reaction applied by the water to the oar then drives the boat forwards.
Swimming
In swimming, the hands apply a force to the water backwards. That is the action.
The water then applies a force to the body forwards, which is what pushes the swimmer along.
Walking
When you walk, your foot pushes the ground backwards. The reaction applied by the ground to your foot carries you forwards. Walking on ice, or on very slippery ground, is difficult because there is not enough friction to push against.
| Situation | Action | Reaction |
|---|---|---|
| Rowing | Oar pushes water back | Water pushes oar forward |
| Swimming | Hands push water back | Water pushes body forward |
| Walking | Foot pushes ground back | Ground pushes foot forward |
| Balloon | Balloon pushes air down | Air pushes balloon up |
What this shows
The pattern is always the same: you go the opposite way to whatever you push.