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More misconceptions Friction and electrical resistance Catherine Low Rangi Ruru Girls’ School

More misconceptions Friction and electrical resistance Catherine Low Rangi Ruru Girls’ School. Four forces act on Toni and the bike while she rides: weight, support, friction and push.

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More misconceptions Friction and electrical resistance Catherine Low Rangi Ruru Girls’ School

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  1. More misconceptionsFriction and electrical resistanceCatherine LowRangi Ruru Girls’ School

  2. Four forces act on Toni and the bike while she rides: weight, support, friction and push. On the diagram below, draw in arrows to show the directions of ALL FOUR forces acting on Toni and the bike. Label the forces.

  3. SUPPORT FRICTION PUSH WEIGHT /GRAVITY

  4. SUPPORT SUPPORT PUSH FRICTION WEIGHT /GRAVITY FRICTION SUPPORT PUSH WEIGHT /GRAVITY PUSH FRICTION WEIGHT /GRAVITY

  5. FRICTION Static • Surface friction Kinetic • Fluid friction/Drag

  6. Common phrase: FRICTION OPPOSES MOTION More correct: (surface) FRICTION OPPOSES SLIDING Drag opposes the relative motion of the object through the air

  7. sliding KINETIC FRICTION STATIC FRICTION Kinetic friction Direction object WOULD slide if there was no grip Static friction

  8. SUPPORT STATIC FRICTION FRICTION DRAG PUSH WEIGHT /GRAVITY

  9. Constant speed Accelerating braking

  10. Rolling resistance Support force Direction of motion

  11. Rolling resistance Direction of motion Overall support force

  12. SUPPORT STATIC FRICTION DRAG WEIGHT /GRAVITY

  13. SUPPORT • STATIC FRICTION • GRIP • TRACTION • DRAG • RESISTANCE WEIGHT /GRAVITY

  14. SUPPORT DRAG STATIC FRICTION WEIGHT /GRAVITY

  15. Explain how the effect of the spikes on the sport shoes changes the effect of forces acting on the athlete and how this leads to an improvement in performance. Answer: Spikes on shoes increase the effect of friction. Resulting in a greater reaction/push/thrust force.

  16. ELECTRICAL RESISTANCE R = Slope of the V vs I graph OR

  17. Ohmic conductors – not an issue V I

  18. The diagram below is a graph showing the voltage – current characteristics of a particular diode. State what physical quantity is represented by the gradient of the graph line. Answer: Resistance

  19. Resistance = how hard it is to push charges through the device

  20. V V V I I I

  21. Halliday, Resnick, Walker

  22. Serway

  23. Direction you want to go STATIC FRICTION Direction of sliding

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