Physics·General Physics · NSSCO 2.9
Friction
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Friction is the force that quietly touches everything you do — it lets you walk without slipping, stops your bike, and slowly wears out your shoes. In this lesson we discover what friction is and where it comes from, how it depends on the surfaces, the heat and wear it always produces, when it helps us and when it's a nuisance, and the clever ways we reduce it. Then we meet friction in the air — drag — and the beautiful idea of terminal velocity.
What you'll learn in this lesson
By the end you should be able to (NSSCO Physics 2.9):
- Describe friction as a force that opposes motion between two surfaces in contact
- Explain how friction depends on the surfaces (how rough they are and how hard they are pressed together)
- Describe the two effects friction always produces — heat and wear
- Discuss the advantages (useful friction) and disadvantages (nuisance friction) of friction in everyday life
- Describe how to reduce friction — lubrication, rollers and ball bearings, streamlining and smoothing surfaces
- Describe air resistance (drag) as friction between a moving object and the air
- Explain terminal velocity qualitatively, when the drag on a falling object becomes equal to its weight
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Ms Elizabeth and Mike talk through the whole topic — with the figure and working drawn live.