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ZingPath: Friction

The Advantages of Friction

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The Advantages of Friction

Physical Science

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Learners explore the advantages of friction in daily life.

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Now You Know

After completing this tutorial, you will be able to complete the following:

  • After completing this Activity Object, learners will be able to:
  • Define friction as the resisting force acting between bodies that tends to oppose motion.
  • Explain that friction can be good or bad, depending on the circumstances.
  • List examples of friction observed in daily life and identify them as advantageous or disadvantageous.

Everything You'll Have Covered

  • The word friction comes from the Latin fricare, which means "to rub." Scientists throughout history have contributed to our understanding of friction. Among the most notable are Leonardo da Vinci, Guillame Amontons, Leonard Euler, and Charles-Augustin de Coulomb. Important laws of friction include the following:
  • The force of friction is directly proportional to the applied load (Amonton's First Law of Friction).
  • The force of friction is independent of the apparent area of contact (Amonton's Second Law of Friction).
  • Kinetic friction is independent of the sliding velocity (Coulomb's Law of Friction).

Friction can be defined as the resisting force acting between bodies that tends to oppose motion. It depends on two variables-the types of surfaces in contact and the force pressing the surfaces against each other. For some time, scientists have explained friction in terms of surface roughness. Some surfaces feel rough, and it is easy to understand how these surfaces would cause friction. Even surfaces that feel smooth to the touch, though, can have bumps and grooves that are observable at the microscopic level. When two surfaces are touching each other, these bumps and grooves stick together, causing microwelds. The greater the force pushing the two surfaces against each other, the stronger the microwelds as more bumps and grooves come into contact. It might be noted that some scientists assert that friction can no longer be attributed to the roughness of surfaces. Instead, they claim, friction is a result of chemical bonding. Scientists of varying opinions admit there are still many unknowns regarding the subject of friction.

We often refer to a few main types of friction-static friction, kinetic or sliding friction, and fluid friction. The causes of friction include surface roughness, molecular adhesion, and deformation effects. Static friction is friction between two solid objects that prevents the objects from moving relative to each other. The coefficient of static friction is typically denoted as Ás and is usually higher than the coefficient of kinetic friction for the same materials. An example of static friction is a heavy box that does not move even when a pushing force is applied. Kinetic, or sliding friction, is the force that opposes motion between two objects moving past each other. The coefficient of kinetic friction is typically denoted as Ák and is usually less than the coefficient of static friction for the same materials. An example of kinetic friction is the resistance presented by a heavy piece of furniture that requires a great deal of force to slide across the floor. Fluid friction is friction between a solid object and a fluid, such as a liquid or gas. An example of fluid friction is the drag on a swimmer in a race.

Tutorial Details

Approximate Time 35 Minutes
Pre-requisite Concepts none
Course Physical Science
Type of Tutorial Concept Development
Key Vocabulary brake, car, engine