Topic 4 : Materials Flashcards
State the meaning tensile forces.
Tensile forces act away from the center of the spring on both directions, and will stretch it out. This is known as an extension.
state the meaning of compressive forces.
Forces acting towards the center of the spring in both directions are called compressive forces.
State the use of Hook’s law.
Hook’s law can be used to model the behaviour of springs or wires when compressive or tensile forces are applied to them.
Define Hook’s law.
Hook’s law states: for a material within its elastic limit, the force applied is directly proportional to the extension of the material.
Express the formula for Hook’s law.
F = k x
What does K stand for in Hook’s law’s equation?
K is the measure of stiffness, and the larger it is, the stiffer the material will be.
State the units for the constant, K?
N/m
When we are using the K constant in our calculations, state the assumption we make.
We must assume that the material is still within the elastic limit.
State whether rubber obeys hook’s law and if it undergoes plastic deformation.
Rubber does undergo elastic deformation but it doesn’t follow hook’s law. It also doesn’t undergo plastic deformation.
Suggest what the area under the loading and unloading curve of rubber represents.
It represents the energy that is required to stretch the material out, which is transferred to thermal energy when the force was removed.
State Whether polystyrene undergo elastic deformation or not and if it follows Hook’s law.
t doesn’t obey Hook’s law, and experiences plastic deformation when any force is applied to it. This makes it very easy to stretch it into new material.
State how you would calculate the K constant when the springs are in series.
In series: K total = Σ (1/kn)
State how you would calculate the K constant when the springs are in parallel.
In parallel: K total = Σ Kn
Explain in terms of energy transfers, what happens during elastic deformation.
When a material undergoes elastic deformation, work is done, and transferred into the material. It is stored in the form of elastic potential energy and is released when the material is allowed to return to its original shape.
State how you could calculate elastic potential energy of a material form a force-extension graph.
To calculate elastic potential energy stored in the material, we can find the area under a force-extension graph.
