Springs Flashcards
What is Hooke’s Law?
Force is directly proportional to extension below the elastic limit.
How would you use a force extension graph to measure the spring constant?
The spring constant is the gradient below the elastic limit.
What is the formula for springs in series?
1/k =1/k1 + 1/k2
What is the formula for springs in parallel?
k = k1 + k2
What is the area under a force extension graph equal to?
The work done to stretch the material or the elastic potential energy stored in the material.
Define tensile stress (σ) and what is its units?
Force per unit cross-sectional area.
Pascals
Define tensile strain (ε) and what are its units?
Extension per unit original length.
No units
Define Young Modulus
The ratio of stress to strain measured in Pascals.
What is the gradient of a stress strain graph?
Young Modulus of the material.
Define elastic behaviour of a spring
When the object returns to its original length when unloaded.
Define plastic behaviour of a spring
When the object’s length is permanently changed. It will not return to its original shape when the load is removed.
Why is there a difference between the area below the loading and unloading curve for a rubber band?
Some of the elastic potential energy stored in the rubber band becomes the internal energy of the molecules.
Why is there a difference between the area below the loading and unloading curve for polythene?
Work is done to deform the polythene permanently as well as the internal energy retained by the polythene when it unstretches.
What is an equation for Young’s Modulus?
E = FL / Ax
