Chapter 6- Materials Flashcards
(18 cards)
What is Hookes law?
The extension of a spring is directly proportional to the force applied. As long as the elastic limit of the spring is not exceeded.
Force constant equation?
F=KX
Define: elastic deformation
Where the spring will return to original shape after the force is removed.
Define: plastic deformation
Where permanent structural change to shape occur and after force is removed it will not return to the original shape.
Describe the experiment to find Hookes constant.
1) set up clamp and spring with weight and measure initial length
2) add weights and for each one added; record the weight,and extension.
Extension = new length - original length
3) plot force against extension.
4) where gradient is straight this is equals to the constant.
How do you find energy stored in a spring?
This equals:
Area under a force extension graph
E= 1/2 FX
E= 1/2KX^2
If you double extension of a spring what happens to the energy given: E= 1/2 k x^2
The energy quadruples
How is a spring combined in series, ie a spring hung to a spring? To find K?
1/k = 1/k(1) + 1/k(2)
How do you find K of a spring in parallel? I.e when 2 spring hold board with weight on.
K= K(1) + K(2)
Define: Tensile stress
Force applied per unit cross sectional area.
What is the unit of tensile stress?
It has the units Pa
Define: tensile strain
Change in length divided by original length.
What is the unit for tensile strain?
Strain has no units- it just a number
What’s the equation for stress?
Stress = force/area
What is the equation for strain?
Strain = extension / original length
What is ultimate tensile strength?
The maximum stress a material can take, it’s the highest point on a stress-strain graph.
Equation for Young’s modulus?
Stress/strain or F x L / E x A
Describe the experiment to find the Young’s modulus
1) set up the experiment where the wire is set up along a table, with a pulley and one end with weights and clamp at the other.
2) you need to measure the cross sectional area of the wire ( several times and find average) and the initial length from end to marker.
3)
