3.4 - Motion - Materials

Question 1

What is meant by the extension of a spring ?

Answer 1

Tensile forces acting away from the centre in both directions stretching out the spring making it extend

Question 2

What is meant by compression of a spring ?

Answer 2

Forces acting towards the centre of the spring in both directions

Question 3

What does Hooke’s law state ?

Answer 3

For a material within its elastic limit the force applied is directly proportional to the extension of the material and once the elastic limit of the material is reached Hooke’s law is no longer obeyed and the material will not return to its original shape.

Question 4

What is Hooke’s law

Answer 4

F is directionally proportional to x
F = kΔx
k = force constant (the stiffness)

Question 5

What is stress ? (tensile)

Answer 5

Force over area (per unit)

Question 6

What is strain ? (tensile)

Answer 6

Extension over original length

Question 7

How is energy stored during elastic deformation

Answer 7

The work done is transferred and stored as elastic potential energy

Question 8

What is the energy change that occurs 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 which causes permanent deformation

Question 9

What is the area underneath a force-extension graph represent

Answer 9

Energy stored in the material

Question 10

Whats the equation that calculates elastic strain energy

Answer 10

E = 1/2 x k x ΔL^2

Question 11

What is youngs modulus

Answer 11

Stress / strain

Question 12

How do you find the young’s modulus from a stress-strain graph

Answer 12

Gradient