Hooke's Law

Question 1

What does Hooke’s Law say?

Answer 1

That extension is proportional to force

Question 2

What is Hooke’s Law as an equation?

Answer 2

ΔF = k Δx

Question 3

What is K in the equation ΔF = k Δx?

Answer 3

Spring constant

Question 4

What are the units for spring constant (k)?

Answer 4

Nm-1

Question 5

Hooke’s Law works just as well for Compressive forces as [……] forces

Answer 5

Tensile

Question 6

What is Point P on the graph (where the line is no longer linear)?

Answer 6

The limit of Proportionality

Question 7

What does the limit of proportionality mean on a graph?

Answer 7

That Hooke’s Law is no longer being obeyed

Question 8

What does it mean when the line on the Force/Extension is straight (linear)?

Answer 8

Hooke’s Law is being obeyed

Question 9

What is point E on the graph?

Answer 9

Elastic Limit

Question 10

What is the elastic limit?

Answer 10

If you exceed the elastic limit the material will be permanently stretched. (plastic)

Question 11

A material will show elastic deformation up to….

Answer 11

its elastic limit

Question 12

A material will show plastic deformation when it is […….] the elastic limit

Answer 12

beyond/greater

Question 13

If deformation is elastic, what happens to the material when the forces are removed?

Answer 13

The material returns to its original shape

Question 14

Describe what happens to the atoms in the material when put under tension.

Answer 14

• When the materials is put under tension, the atoms of the material are pulled apart from one another
• Atoms can move slightly relative to their equilibrium positions
• Once the load is removed, the atoms return to their equilibrium distance apart.

Question 15

What happens to the material if the deformation is plastic?

Answer 15

The material is permanently stretched

Question 16

What happens to the atoms in a material that has exceeded the elastic limit?

Answer 16

• Atoms on the material move position relative to one another
• When the load is removed, the atoms don’t return to their original positions

Question 17

Experiment to Investigate Extension

Answer 17

• Set up equiptment shown in the diagram
• Add weights on at a time to the bottom of the object
• After each weight is added measure the new length on the object.
• Calculate the extension [extension = new length - original length]
• Plot a graph of force (weight) against extension (where the line is linear is were it obeys Hooke’s Law and the gradient = k)
• WEAR SAFETY GOGGLES AND STAND UP WHEN DOING EXPERIMENT