# PJ physics Materials

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- Created by: Amy Davis
- Created on: 03-06-10 14:39

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**PJ PHYSICS AQA AS UNIT 2 Materials**

*Density*

- Density = mass/volume (p=m/v) kgm^-3
- Regular solid: take measurements (height, width, length, mass) then use the equation to find density
- Liquid: weigh in a measuring cylinder then minus the mass of the cylinder, then use equation
- Irregular solid: Weigh, then immerse in water and measure increase in volume, then use equation.

*Hooke's Law*

- Tension is equal and opposite to the force that is stretching the string
- Force needed to stretch the string is propotional to the extension of the string.
- Force = spring constant x extension (F=kl)
- Stiffer springs have a higher k
- if a string is stretched beyond its elastic limit it does not go back to its original length
- If springs are in parallel and the weight is in the exact right place their extensions will be the same. The position depends on the spring constant of each spring. If they are the same the weight can be placed in the exact middle.
- If springs are in series the tension in each one is equal to the weight at the bottom.
- Elastic…

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