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Flashcards in Motion 2 Deck (12):
1

describe tensile and compressive deformation

when an object changes shape (atoms moved from their equilibrium positions) due to tensile forces (pulling) or compressive forces (pushing)
-tensile forces are 'positive' compressive forces are 'negative'

2

outline the differences between elastic and plastic deformation

elastic: object returns to original shape after the forces are removed, atoms move slightly from equilibirum position until force is removed
plastic: object gets permanently stretched, atoms do not return to their original positions after the load is removed

3

what is hooke's law

extension is directly proportional to the force applied, or F=kx
k is the FORCE CONSTANT of the material
most materials obey it up to a point

4

when is a Force - extension graph linear

-when an object obeys Hooke's Law

5

what can you find out from a force - extension graph

-gradient = force constant, k
-area underneath = work done = 0.5Fk = 0.5kx^2

6

describe an experiment to determine the force constant of a spring/wire

-

7

define strain

extension/original length (no units)

8

what are the typical stress strain graph features for
-a brittle material
-a ductile material
-a polymer

brittle: linear until a point, then becomes curved at the limit of proportionality. when the graph stops it breaks
ductile: linear for only a very small amount of strain, then becomes curved. breaks much later than a brittle material
polymer:

9

how can you experiment to find the young modulus of a wire

-must be a very long, thin wire

10

what is the Ultimate Tensile Strength of a material

-the maximum stress it can withstand before breaking
-the highest point on its stress - strain graph

11

what is the elastic limit of a material

the a point on a force - extension graph where exceeding it will mean the material will be permanently stretched if the force is removed

12

what is the elastic limit of a material

the a point on a force - extension graph where exceeding it will mean the material will be permanently stretched if the force is removed