Newton’s third law states that for every action, there is an equal and opposite reaction. When applied to a fish swimming through water, the law can be broken down as follows:
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Pushing Water Backwards: When the fish uses its fins to push water backwards, this is the action force. The fish generates thrust by moving its fins and body, creating a pressure difference.
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Water's Reaction Force: According to Newton's third law, as the fish pushes the water backwards, the water pushes the fish forward. This forward push is the reaction force that propels the fish through the water.
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Swallowing and Expelling Water: When a fish swallows water, it can create a jet of water by expelling it forcefully (spitting it out). The action of the fish expelling water creates a reaction force that moves the fish forward.
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Wiggling Fins: When the fish's fins wiggle, they create a force against the water. The water, in turn, pushes back against the fins with an equal and opposite force, causing the fish to move forward.
Overall, in all these scenarios, the interaction between the fish and the water showcases the principles behind Newton's third law, where the actions of the fish lead to a corresponding reaction in the water, allowing the fish to swim effectively.