Material

Question 1

High winds produce a large amplitude to vibrations of wire, explain why the wire might sag when high wind stops

Answer 1

• Copper may be stretched past elastic limit

- permanent deformation.

Question 2

What does the area under a stress-strain graph give?

Answer 2

Elastic strain energy per unit volume

Question 3

What does the area/ gradient under a force-extension graph give you?

Answer 3

Area- Elastic strain energy

Gradient - stiffness

Question 4

The gradient of stress-strain graph gives?

Answer 4

The Young’s modulus

Question 5

What is the units for strain?

Answer 5

There are no units as it’s a ratio.

Question 6

Behaviours:
Elastic
Plastic
Brittle

Answer 6

1) The material returns to its original shape + size when the force is removed. (Energy used to deform the material is stored as elastic strain energy.)
2) Material realms permanently deformed (work is done to deform the material, releasing heat.)
3) The material fractures (breaks) before any elastic deformation takes place.

Question 7

the wire were coiled to form a spring, and this was used to suspend a mass, describe how energy [4] would be transferred between kinetic, gravitational potential and elastic strain forms when the mass
moves up and down

Answer 7

Solution:
Total energy is always conserved.
At the top of its range, kinetic energy and elastic strain energy are zero; all energy is GPE. As the mass falls, its initial GPE is transferred to elastic strain energy and kinetic energy. Kinetic energy is at a maximum half way through the fall. At the bottom, GPE is zero, kinetic is zero; all energy is elastic strain.

Question 8

Energy stored on the spring

Answer 8

1) is equal to energy stored by the spring

2) work done = F (ave) x distance = 1/2 F(max) x e