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Physics Homework help Stress, strain and YM questions. Very Hard (I think) AS level watch

1. Q37) What Stress would cause a wire to increase in length by one-tenth of one percent f the Young Modulus for the wire is 12x10 to the 10. What force would produce this stress if the diameter of the wire is 0.56mm?

Q40) A massive stone pillar 20m high and of uniform cross section rests on a rigid base and supports a vertical load of 5.0x10 to the 5 N as its upper end. State, with reasons, where in the pillar the maximum compressive stress occurs. If the compressive stress in the pillar is not to exceed 1.6x10 to the 6 N/m^2, what is the minimum cross sectional area of the pillar? density of stone = 2.5x10to the 3 kgm^3?

Anyone else doing AQA Physics A, and doing the same topic? How are you finding it?
2. Qu37
Young Modulus = stress / strain
strain is fractional change in length
You are given strain as a % and the modulus.

You now have the stress
stress = force/area
you are given the area (via the diameter - be careful with the units!)
3. so, stress is equal to 1/ 0.1*YM??
4. I do A2 physics, and it gets MUCH harder than stress, strain and youngs modulus, just sayin' :P brace yourself!
5. (Original post by Hiya123321)
so, stress is equal to 1/ 0.1*YM??
Stress = Young Modulus x one tenth of a % (as a fraction)
6. Thank You.

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