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What is force? |
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Any push or pull that tends to cause a change in
motion |
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measured in Newtons (N) or pounds (lbs) |
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1 N = 0.225 lbs |
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examples of force |
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gravity (weight) |
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magnetism |
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electricity |
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tension or compression |
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1st Law - Law of Inertia |
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An objects motion will remain constant as long
as the forces are balanced. |
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2nd Law - F = ma |
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The net force on an object will cause it to
accelerate inversely proportional to its mass |
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3rd Law - Action - Reaction |
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For every action there is an equal but opposite
reaction |
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Forces are balanced (1st law) |
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The net force (resultant force) is 0 |
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There is no change in motion |
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a = 0 |
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v is constant |
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Friction is dependant on 2 factors, the
roughness of the surfaces (coefficient of friction) in contact and the
force pushing the surfaces together (normal force) |
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1. What is being asked for ? |
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2. What is given ? |
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3. What facts (formula) relate what is asked
with what is given. MAKE SKETCH ! |
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4. Substitute |
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5. Calculate |
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CHECK THE ANSWER ! |
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Does it answer the question ? |
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Does it make sense ? |
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Is there a need for rounding ? |
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For 3 forces |
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sketch a free-body diagram |
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draw a force triangle |
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use trigonometry |
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if right triangle |
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sin, cos, tan |
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if not |
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law of sines |
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law of cosines |
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OR Create a scale drawing |
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More than 3 forces |
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sketch a free body diagram |
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break forces into components if necessary |
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write equations for SFx = 0 and SFy
= 0 |
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include friction if needed F = m N |
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Notes