3.4 Materials

Question 1

What is extension and compression of a spring?

Answer 1

Tensile forces act away from the centre of the spring in both directions and will stretch it out causing the spring to extend

Question 2

What happens to the spring when tensile/compressive forces are exerted?

Answer 2

The spring undergoes ‘tensile deformation’ (for tensile forces) or ‘compressive deformation’ (for compressive forces)

Question 3

What is Hooke’s law?

Answer 3

In a material showing Hooke’s law, the force applied is directly proportional to the extension in lenght, up to the limit of proportionality
F=kx

Question 4

What is meant by tensile stress?

Answer 4

The force per unit area

Question 5

What is tensile strain?

Answer 5

A measure of how the material stretches:the extension divided by the original length. This value is a ratio, so it has no units

Question 6

What is the difference between elastic and plastic deformation?

Answer 6

Elastic deformation:when the force is removed the object will return to its original shape
Plastic deformation: after the force is removed, the object will not return to its original shape (limit of proportionality has been exceeded)

Question 7

How is energy stored during elastic deformation?

Answer 7

The work done is transferred and stored as elastic potential energy

Question 8

Describe the energy changes that occur during plastic deformation

Answer 8

The material is stretched and the energy from the work done is used to break the bonds between the molecules. This causes permanent deformation