I know the wind off the ocean pushes the water and makes waves on the beach, but when the wave comes in, what makes it go back out?
In: Physics
Gravity. Beaches are uphill from the water. The wind pushes the wave hard enough for it to temporarily move uphill but water is heavy so it quickly flows back downhill.
Gravity.
The waves are causing the water to flow in, slightly uphill. When the friction against the land stops them, gravity pulls the water back down the slop into the sea.
Stand at the middle of a slope and chuck a bucket of water at the slope and see where the water goes.
You are the wind and you’re chucking water up the slope but gravity pulls it back down.
Gravity and pressure.
As the swells break onto the beach, they are pushing water onto the shore, which is higher than the water. Gravity starts to pull it back down, which is what you see when each wave retreats back into the water. That area can’t keep receiving more water, however, as the weight of the water becomes higher than the pressure of the new water coming in. Some of it has to escape to areas of lower pressure. This is why you get rip tides. The water being pushed into shore will travel to an area of lower pressure, then go back out to the ocean through a small current called a rip tide. There are always some outward currents, however. Even in calm weather they are minor and may not be powerful enough to pull you out to sea if you get caught in one. If the waves are higher and are occurring with higher frequency (or if the geography is right even on calm days) rip tides can get strong enough to overcome even a very good swimmer. That’s why you should always be careful, even when it doesn’t seem dangerous.
Latest Answers