Springs, Young modulus

Question 1

Limit of proportionality

Answer 1

Up to this point the material obeys Hooke’s law. Extension is proportional to the force applied

Question 2

How is Hooke’s law is shown on a force/extension graph?

Answer 2

Straight line through the origin

Question 3

Elastic limit

Answer 3

The point after which the material will not return to it original shape when the force is removed

Question 4

Plastic material

Answer 4

A material, which will not return to its original shape after the force is removed from it

Question 5

Ultimate tensile strength

Answer 5

Maximum amount of stress that can be applied to a material without making it break

Question 6

Breaking point

Answer 6

The point where material breaks

Question 7

Breaking Stress

Answer 7

Stress applied to material that causes it to snap/break

Question 8

Equation of breaking stress

Answer 8

Breaking stress = breaking force/(initial length * section area)

Question 9

What happens to the spring constants of springs in series

Answer 9

Ktotal=K1+K2

Question 10

What happens to the spring constants of springs in parallel

Answer 10

1/Ktotal=1/k+1/k

Question 11

Equation linking force, extension and spring constant

Answer 11

F=ke or F=kx

Question 12

Equation linking word done, force and extension

Answer 12

WD=1/2F*e

Question 13

Britle

Answer 13

A material which snaps once enough stress is applied ie doesn’t bend

Question 14

Ductile

Answer 14

A material that can be bent into a shape of a wire

Question 15

Polymeric

Answer 15

A material that has a very large strain, but low stress

Question 16

In an elastic band where does the energy lost go?

Answer 16

Friction between the molecules (heat)

Question 17

Hysteresis

Answer 17

Area between the loading and the unloading part of the force/extension graph

Question 18

Stress

Answer 18

Force per unit area

Question 19

Strain

Answer 19

Change in length per original length

Question 20

Stress equation

Answer 20

=F/A

Question 21

Strain equation

Answer 21

=Extension/original length

Question 22

Units of stress

Answer 22

Pa

Question 23

Units of strain

Answer 23

No units

Question 24

Young modulus equation

Answer 24

=Stress/Strain

Question 25

What do tensile forces do?

Answer 25

Stretch the object

Question 26

What do compressive forced do?

Answer 26

Squash the object

Question 27

Hooke’s Law

Answer 27

The extension of a spring is directly proportional to the force applied until the elastic limit is exceeded

Question 28

Why is energy stored in stretched springs

Answer 28

A force has been applied to the spring to move it through a distance → force has done work → WD=FD → force in spring =ke → WD proportional ke^2

Question 29

Equation linking work done, spring constant and extension

Answer 29

W=1/2ke^2

Question 30

Equation linking work done, spring constant and force

Answer 30

W=1/2 * (F^2)/k

Question 31

Plastic deformation

Answer 31

When loading off a spring it doesn’t return to its original length as the elastic limit has been passed, permanent change in length

Question 32

How to determine a Young Modulus of a wire? (5)

Answer 32

1. Use a micrometer at several points to find the diameter, take the average
2. Clamp the wire at one end and suspended taught using a pulley at the other end
3. Place a ruler parallel to the wire with a fiducial marker placed so that the extension of the wire can be measured
4. Apply different forces
5. Plot a graph and calculate YM using the formula