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