1.5 Solids under stress - Rubber

What does the gradient of the stress-strain graph represent?

• Load on the material

• Energy per unit volume

• Stiffness of the material

• Elasticity of the material

What is the structure of natural rubber like?

• Long chain molecules with occasional cross-linking

• Short chain molecules with no cross-linking

• Spherical molecules with no cross-linking

• Randomly arranged molecules

What is the difference between a force-extension graph and a stress-strain graph for the same material?

• Different values and units on the axes

• Different shapes of the curves

• Different colors of the lines

• Different scales on the axes

What happens to the stiffness of rubber as it is stretched?

• Gradually increases

• Gradually decreases

• Fluctuates randomly

• Remains constant

What is the term used to describe the behavior of a stress-strain graph when a load is removed?

• Hysteresis

• Elasticity

• Plasticity

• Viscosity

What does the shaded area in the stress-strain graph represent?

• Stiffness of the material

• Elasticity of the material

• Energy per unit volume

• Load on the material

What effect does hysteresis have on rubber?

• Causes material to become more elastic

• Transfers energy to its molecules, resulting in heating

• Reduces energy absorption

• Increases material rigidity

What can happen if a car tyre goes through hysteresis due to under-inflation?

• Increased fuel efficiency

• 'Blow-out' when the air inside the tyre becomes hot

• Improved traction on the road

• Decreased pressure in the tyre

How do modern, energy-efficient tyres reduce the problem of hysteresis?

• Using rigid rubber for the tyre walls and flexible rubber for the tread

• Using flexible rubber for the tyre walls and rigid rubber for the tread

• Using the same type of rubber for both tyre walls and tread

• Not using rubber in the tyre construction

What is the primary function of most tyres using the same rubber for two different jobs?

• Provide elasticity for the tyre wall and rigidity for the tread

• Provide rigidity for the tyre wall and elasticity for the tread

• Provide rigidity for both the tyre wall and tread

• Provide elasticity for both the tyre wall and tread