Hooke's Law
Slides do conjunto (3)
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- States: The force(F) needed to extend or compress/extend a spring or elastic body by some distance x scales linearly with respect to that distance up to the limit of proportionality
- Symbolic: F∝x
- Equation: F=kx
- where k is the stiffness of the object = Nm-1
- SI units: kgms-2=k m
- Say a spring has stiffness constant k, and a weight of 1kg hanging off of it and due this moves distance x
- In series, this is 0.5k, 1kg and 2x
- In parallel, this is 2k, 1kg and 0.5x
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- Elastic
- Up to the limit of proportionality
- Material returns to original shape
- Tension = atoms pulled apart = moving slightly from equilibrium position, no tension = atoms return to equilibrium distances apart
- Plastic
- Beyond the limit of proportionality
- Material does not return to original shape
- Tension = atoms pulled apart = move position in material, no tension = atoms remaining in this position
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- Equipment: Clampstand, clamp, meter ruler, object, weights
- Clamp the object, measure its length and add weights one at a time to the bottom of the object
- After each weight, measure the new length and calculate extension = new length - original length
- Plot the graph of Force vs. extension
- Where the line is straight, Hooke's law is obeyed, therefore gradient = k
- If you load object with weight beyond the limit of proportionality, the line will curve down
- Safety: stand whilst performing to get out of the way if the object falls, safety goggles in case object snaps