More misconceptions Friction and electrical resistance Catherine Low Rangi Ruru Girls

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More misconceptionsFriction and electrical
resistanceCatherine LowRangi Ruru Girls School
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• 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.

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SUPPORT
FRICTION
PUSH
WEIGHT /GRAVITY
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SUPPORT
SUPPORT
PUSH
FRICTION
WEIGHT /GRAVITY
FRICTION
SUPPORT
PUSH
WEIGHT /GRAVITY
PUSH
FRICTION
WEIGHT /GRAVITY
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FRICTION

• Static
• Surface friction
• Kinetic
• Fluid friction/Drag

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

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• KINETIC FRICTION
• STATIC FRICTION

sliding
Kinetic friction
Direction object WOULD slide if there was no grip
Static friction
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SUPPORT
STATIC FRICTION
FRICTION
DRAG
PUSH
WEIGHT /GRAVITY
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Constant speed
Accelerating
braking
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Rolling resistance
Support force
Direction of motion
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Rolling resistance
Direction of motion
Overall support force
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SUPPORT
STATIC FRICTION
DRAG
WEIGHT /GRAVITY
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SUPPORT

• STATIC FRICTION
• GRIP
• TRACTION

• DRAG
• RESISTANCE

WEIGHT /GRAVITY
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SUPPORT
DRAG
STATIC FRICTION
WEIGHT /GRAVITY
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• 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.

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ELECTRICAL RESISTANCE

• R Slope of the V vs I graph
• OR

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Ohmic conductors not an issue
V
I
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• 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

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• Resistance how hard it is to push charges
  through the device

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Halliday, Resnick, Walker
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Serway
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Direction you want to go
STATIC FRICTION
Direction of sliding