BTH-Materials

Question 1

Define density

Answer 1

measure of how much mass an object has per unit volume

Question 2

Give the formula for density including units

Answer 2

ρ=m/v where density is measured in kg/m^3, mass is kg and volume is m^3

Question 3

State the equation for Hookes law and include units

Answer 3

F=kx where F is measured in Newtons, k is N/m and x is in meters

Question 4

Define elastic limit

Answer 4

Maximum force the spring can sustain and then return to zero extension

Question 5

Define stress

Answer 5

The force acting on the unit area of the material

Question 6

Give the formula of stress with units

Answer 6

σ = F/A where stress is measured in Nm^2 or pascals

Question 7

When is stress positive or negative?

Answer 7

tensile force=positive stress and a compressive force=negative stress

Question 8

Define strain

Answer 8

The measure of the deformation of a material under stress

Question 9

Give the formula for strain and include units

Answer 9

Strain=ΔL/L0 where is strain HAS NO UNITS

Question 10

When is strain positive or negative?

Answer 10

tensile force=positive strain , compressive force=negative strain

Question 11

Define elastic strain energy?

Answer 11

Energy stored in a material when it is deformed elastically

Question 12

How can elastic strain energy be determined?

Answer 12

The area underneath a force-extension graph

Question 13

Define ultimate tensile stress

Answer 13

maximum tensile stress an object can withstand

Question 14

How can you identify areas of plastic behaviour on a graph?

Answer 14

Look to the right of the elastic limit point

Question 15

What is brittle behaviour?

Answer 15

An object is brittle if it suddenly breaks/cracks

Question 16

Give the formula for elastic potential energy.

Answer 16

E=1/2FΔL. . . .E=1/2K(ΔL)^2

Question 17

What is a force that causes an increase in length called?

Answer 17

Tensile force

Question 18

Give the 3 factors the stiffness of a material depends on

Answer 18

material, length, cross-sectional area

Question 19

Give the cross sectional area formula

Answer 19

A=πd^2/4

Question 20

Give the young modulus formula and units

Answer 20

E=Fx/AΔx or E = σ / ϵ

Question 21

Give Hookes law statement

Answer 21

Up to a given load, the extension of a spring is directly proportional to the force applied

Question 22

State the gravitational field strength

Answer 22

9.81NKg^-1

Question 23

give the work done formula with units

Answer 23

W=FΔx or W=1/2max force x extension(changes to W=1/2kΔx^2)

Question 24

Give a way to calculate work done without formula

Answer 24

The area under the graph

Question 25

Define Hardness

Answer 25

A hard material is difficult to indent or scratch

Question 26

Define stiffness

Answer 26

A subject that exhibits very small deformations even when subject to large forces

Question 27

Define Brittleness

Answer 27

Brittle objects will shatter or crack on impact. These objects experience very little plastic deformation

Question 28

Define strength

Answer 28

A strong object can withstand a large force before it breaks (dependent on size)

Question 29

Define malleability

Answer 29

A malleable material can be hammered into shapes = experience plastic deformation

Question 30

Define a ductile material

Answer 30

A ductile material can be drawn into wires and experience plastic deformation