Hooke's Law

Question 1

Recall and use the equation for an object under tension

Answer 1

• 𝐹 = 𝑘𝑥

Question 2

State that an object with constant stiffness k will:

Answer 2

• Obey Hooke’s Law

Question 3

Appreciate which materials – and under which conditions – obey Hooke’s law

Answer 3

• Metals and springs obey Hooke’s Law provided the limit of proportionality has not been exceeded
• Glass always obeys Hooke’s Law provided it hasn’t broken - it is brittle
• Rubber does not obey Hooke’s Law

Question 4

Appreciate what type of quantity k is
There exists a related quantity called the Young
modulus - what type of quantity is this

Answer 4

• K is an extrinsic property, it depends on dimensions
• A spring/wire with a larger cross sectional area becomes more stiff - k increases
• If the spring/wire is longer then k decreases
• Young’s modulus is an intrinsic property which doesnt change with dimensions