Materials

Question 1

What is breaking stress?

Answer 1

The stress required to break a material

Question 2

What happens when a spring goes past the elastic limit?

Answer 2

The spring becomes permanently stretched.

Question 3

What is another unit for Pa (Pascal)

Answer 3

Nm^-2

Question 4

What is the unit for Tensile Stress?

Answer 4

Pa (Pascal)

Question 5

What is the spring constant rule for springs in series?

Answer 5

1/keff = 1/k1 + 1/k2

Question 6

What is the spring constant rule for springs in parallel?

Answer 6

keff = k1 + k2

Question 7

Define Young Modulus

Answer 7

A measure of the stiffness of a material

Question 8

What does it mean if a material is brittle?

Answer 8

It snaps without stretching or breaking when subject to stress.

Question 9

What is the equation for density?

Answer 9

Mass/volume

Question 10

What happens when a spring is behaving elastically?

Answer 10

Up to a certain extension, if the force is removed the spring will return to its original position.

Question 11

What is spring constant and what is its unit?

Answer 11

The force required to produce an extension of one metre.

Unit is Nm^-1

Question 12

What is the equation relating extension and force?

Answer 12

F = k x delta L

Question 13

What is the unit for density?

Answer 13

kgm^3

Question 14

What is Hooke’s Law?

Answer 14

The force needed to stretch a spring is directly proportional to the extension of a spring from its natural length. Up to the limit of proportionality.

Question 15

What is breaking stress?

Answer 15

The stress required to cause a material to break.

Question 16

What happens when a string becomes permanently stretched?

Answer 16

Plastic behaviour occurs and Hooke’s Law is no longer obeyed by the spring.

Question 17

What is the equation for tensile stress?

Answer 17

Tensile force / cross-sectional area

Question 18

Stretching force is also called what?

Answer 18

Tensile force

Question 19

In a force/extension graph, what is represented by the area under the graph?

Answer 19

Work done.

Question 20

What does the unloading line look like on a force/extension graph for a metal wire that has been stretched beyond its limit of proportionality?

Answer 20

Parallel to the straight section of the loading line going down to the x axis.

Question 21

Why does the unloading line of a force/extension graph have a non zero intercept and why is it parallel to the loading line?

Answer 21

Plastic deformation has produced permanent extension hence intercept is non zero.
The gradient is the same because after extension there is still the same forces between bonds as there were during loading.