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Friction and Traction. Unit 8. Friction. A force that works against motion. Static Friction – friction between 2 objects not in motion. Kinetic (sliding) Friction – friction between 2 objects that are in motion.
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Friction and Traction Unit 8
Friction • A force that works against motion. • Static Friction – friction between 2 objects not in motion. • Kinetic (sliding) Friction – friction between 2 objects that are in motion. • Once an object has overcome that initial push (or static friction), it has kinetic friction.
Friction • There are 2 factors that determine the amount of frictional force that can occur between 2 surfaces: • The coefficient of friction • The normal force Ff = uFN
Coefficient of Friction • Describes the grippyness of 2 surfaces sliding against one another. • Slippery objects have a low coefficient of friction while sticky objects have a high coefficient. • The coefficient can range from 0 – 1.
Normal Force • Force that presses 2 sliding surfaces together. • Is equal and opposite to gravity or the weight of an object.
Traction • The friction between the wheel and the surface it moves on. • It is the amount of force a wheel can apply to a surface before it slips. • To increase traction you must either • Increase the coefficient of friction (between the wheel and the surface). • Increase the normal force (the weight of the robot).
Friction in VEX • Different wheels have different traction • Plastic on plastic parts reduces friction. Metal on metal is not desirable for moving systems.
Tasks • THINK Phase – keyterms and notes • BUILD Phase – pp. 27-34 • AMAZE Phase – Challenge on p. 36. Take note of modification ideas. 4. Engineering Notebook p. 37 5. STEM – all 6. Skills Logbook – new skills acquired and new skills to work on. 7. Group and Self Assessments