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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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gravitational (weight) |
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magnetic |
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electrical |
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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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An
objects motion will remain constant as long as the forces are balanced |
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What is inertia ? |
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Equilibrium |
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S F = 0 |
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Constant motion |
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a = 0 |
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v is constant |
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vf = vi |
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Balanced
forces means that the sum of the force added together is zero. The object
is said to be in equilibrium. |
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Forces
are vectors. When adding vectors there are several methods that can be
used. |
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Graphical |
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polygon or parallelogram |
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Analytical |
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component or law of sines / law of cosines |
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sine |
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cosine |
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tangent |
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Pythagorean Theorem |
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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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English Units |
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pounds for force |
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slugs for mass |
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ft/sec2 for acceleration |
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1lb. = 1 slug·ft/s2 |
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Metric Units |
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newtons for force |
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kilograms for mass |
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m/sec2 for acceleration |
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1N = 1 kg·m/s2 |
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Weight - the force due to gravity |
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Mass - the amount of matter |
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For
every action there is an equal but opposite reaction |
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these force do NOT cancel each other because
they act on different objects |
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in the picture below, the force of the hammer on
the nail is the same as the force of the nail on the hammer. |
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Notes