PAG 2.3 Investigating Properties Of A Plastic Flashcards
What is the disadvantage of cutting a hole to hang the plastic from?
This will result in a stress concentration when it is loaded. This means that the stress isn’t evenly distributed thoughtout the plastic
What is breaking stress?
The stress at which the material will break apart
How can the work done to permanently deform a material be obtained?
Given by the area between the loading and unloading lines on a load-extension graph
What is plastic deformation?
Where the object will remain permanently deformed when the deforming forces are removed
What is the elastic limit?
The point beyond which the sample no longer deforms elastically and so no longer returns to its original shape when the deforming forces are removed. Beyond this point, plastic deformation occurs
How can the data to plot an unloading line be obtained?
The masses can be removed one by one and the extension measured each time
Why will the load-extension graph not be a straight line graph for this experiment?
Plastics do not deform elastically and so don’t obey Hooke’s law. The samples will deform plastically and will produce a curved graph
How can the force applied by a mass be calculated?
Force will equal the weight of the mass
F=mg
How do you calculate a sample’s extensions?
Extension= extended length - original length
What safety precautions should be taken when carrying out this experiment?
Ensure that the masses are hanging over the workbench. Place padding beneath them so that they don’t bounce and cause injury when they fall
How should the length measurements be taken?
From the same point each time. A ruler can be used and when taking the measurements, it should be read at eye-level to reduce parallax error
