Materials

Question 1

When 2 identical springs are in parallel, what is the extension?

Answer 1

Half the extension of 1

Question 2

When 2 identical springs are in series, what is the extension?

Answer 2

Double the extension of 1

Question 3

Total spring constant of springs in parallel

Answer 3

K = K1 + K2…

Question 4

Total spring constant of springs in series

Answer 4

1/K = 1/K1 + 1/K2…
K = (1/K1 + 1/K2..)*-1

Question 5

Equations for calculating work done to stretch a spring

Answer 5

W = 1/2Fx
Or
W = F*2 / 2k

(Can’t just use W=Fx because F may not be a constant)

Question 6

Explain the shape of a force-extension graph for rubber

Answer 6

Hysteresis loop

There is more work done when loading then unloading as energy dissipates as thermal energy when unloading

Question 7

What is the area under a force-extension graph

Answer 7

Elastic potential energy or work done

Question 8

What is plastic behaviour

Answer 8

Permanent deformation when the load is removed

Question 9

What is elastic behaviour?

Answer 9

When the material returns to its original shape when the load is removed

Question 10

What is fracture stress?

Answer 10

The stress needed to cause something to break

Question 11

What is yield stress?

Answer 11

The stress needed to cause something to permanently deform

Question 12

What does stiff mean?

Answer 12

Resistance to deformation

Question 13

What does brittle mean?

Answer 13

When cracks propagate easily and fracture occurs readily

Question 14

What does tough mean?

Answer 14

Resistance to the formation and propagation of cracks

Question 15

What does hard mean?

Answer 15

Resistance to scratching and deformation upon impact

Question 16

What does ductile mean?

Answer 16

Can be drawn into wires and deforms plastically in response to stress

Question 17

What does malleable mean?

Answer 17

Can be bent or hammered into shape

Question 18

Equation for stress?

Answer 18

Force (N) / Cross-sectional area (m*2)

Stress (Nm*-2)

Question 19

What does Young’s modulus tell you

Answer 19

The stiffness of a material
(Can only find up to limit of proportionality - as it’s the gradient)

Question 20

How to calculate Young’s modulus

Answer 20

Stress / strain

Question 21

How to calculate Young’s modulus

Answer 21

1. Set up apparatus
2. Measure diameter of a wire at multiple points using a micrometer
3. Calculate the mean and find the area of the wire (A= πr²)
4. Measure as large of an original length as possible (i.e 1m) and mark clearly
5. Place a ruler set at 0 at the original length (to measure extension directly)
6. Apply a known mass or force to the wire/pulley system
7. Ensure the wire has stopped extending and measure the change in extension
8. Repeat steps adding more mass each time
9. Draw a graph of force against extension
10. Gradient = EA/L
11. Young’s modulus = Gradient x L / A

Question 22

What is Hookes law?

Answer 22

Force is directly proportional to change in length (up to the limit of proportionality)
F=kx