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Imagine visiting the beach, and then walking through the sea water.
With the seawater up to your knees, you would probably notice that walking through the water is more difficult than walking normally. Why is that?
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That's because of the force of water resistance slowing down your movement. Let's learn about this force!
Water resistance is a force that an object moving through water experiences. We sometimes call water resistance drag. Water resistance always acts against the movement of the object, in the opposite direction.
Water resistance happens because the object moving through the water has to 'push' water particles out of the way, to move through. This is why it can feel difficult to wade through water.
Water resistance is a type of friction - remember, friction happens as a result of surfaces rubbing over each other.
Water resistance is a contact force. It is a contact force because there is contact between the solid particles of the object and the liquid particles in the water.
Earlier, we said that a person swimming experiences water resistance. When someone swims, their arms and legs cause a forward force, moving the swimmer forwards.
However, the swimmer has to 'push' past the water particles in the pool - this causes the force of water resistance. The direction of the water resistance is backwards in this case because water resistance always acts in the opposite direction to the direction of movement.
The greater the water resistance, the slower the person can swim.
What factors affect the size of the water resistance force?
Two important variables affect air resistance.
1. The greater the surface area of an object, the greater the water resistance. A large surface area means that more force is needed to push past the greater number of water particles in the way.
2. The greater the speed of the object, the greater the water resistance.
Now that we have a good understanding of water resistance, let's try some questions!
