Friction
From the Simple English Wikipedia, the free encyclopedia that anyone can change
Friction is a force that acts to stop the movement of two touching things. Friction also makes heat. Two types of friction are static and kinetic. Static friction acts when objects are not moving, or when they are not sliding against one another. Kinetic friction acts when objects are sliding against one another. Facts about friction include:
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Friction is caused by imperfections on the surfaces of two materials. These imperfections are called asperities. As these two rough surfaces move against each other they get stuck and prevent motion until broken or slid over. Even the smoothest of materials have these asperities.
Model of asperities
- As the force that is pushing on the object increases, the static friction increases too. However, after a while the force will get bigger until it matches the maximum static friction making the object begin to move. The object will begin to move at the split second the static friction is less than the force pushing on it. After that point kinetic friction will start affecting the object.
- The coefficient of friction is the value between two things and the force putting them together. For example, a person's skates on ice has a low coefficient of friction, but rubber on concrete has a high one.
- Internal friction in a fluid is called viscosity. This is basically how easy it is for the fluid to move or flow. For example honey is more "viscous" than water. A factor that can alter viscosity is temperature.
- Laminar flow is when two layers of fluids flow over each other.
