Chapter 4 Materials (4.1)

Question 1

Density formula?

Answer 1

Density = mass / volume

Question 2

What is upthrust?

Answer 2

When an object is submerged in fluid it experiences up thrust.

The size of the up thrust will be equal to the weight of the fluid that has been displaced

This is referred to as Archimedes’ principle

Question 3

Equation for mass of fluid displaced?

Answer 3

Volume of object x density of fluid

Question 4

When will on object float?

Answer 4

When liquid displaced = weight of object

Question 5

What is a hydrometer?

Answer 5

A piece of equipment that is used to determine the density of a fluid.

Question 6

How does a hydrometer work?

Answer 6

The device has a constant weight that will sink lower in less dense fluids. This is because volume of less-dense fluid must be displaced by the weight of the hydrometer for it to float.

Scale markings on the hydrometer indicate density.

Question 7

How can a hydrometer determine how alcoholic a drink is?

Answer 7

The more alcohol content the lower the density.

Question 8

What is laminar flow?

Answer 8

Laminar flow generally occurs at lower speeds. Laminar flow is characterized by fluid particles following smooth paths in layers, with each layer moving smoothly past the adjacent layers with little or no mixing

Question 9

What is streamlining?

Answer 9

The line of laminar flow are called streamlines. Streamlines are lines of laminar flow in which the velocity is constant over time

Question 10

What is turbulent flow?

Answer 10

Where fluid velocity in a particular place changes over time, often in an unpredictable manner

Question 11

Why do you find it harder to walk in water than through air?

Answer 11

The friction acting against you in water is greater than it is in air (Viscosity of the water)

Question 12

If a liquid is extremely viscous. Is it faster or slower than a less viscous liquid?

Answer 12

Slower

Question 13

What is viscosity?

Answer 13

Viscosity is essentially how resistant a fluid is to flowing.

Question 14

What is the coefficient of viscosity?

Answer 14

Value given to a fluid to indicate how much it will resist flow

Question 15

What is terminal velocity?

Answer 15

When an object falling reaches equilibrium between the weight and the sum of up thrust and drag

Question 16

When is an object at terminal velocity ?

Answer 16

When it is no longer accelerating but instead falling at a constant velocity

Question 17

What is Stokes law?

Answer 17

F=6(Pie)(radius of sphere)(n (coefficient of viscosity in fluid))(terminal velocity)

Question 18

Equation combining stokes law with weight?

Answer 18

Weight = Weight of fluid displace + Stokes Law

Question 19

What is viscous drag?

Answer 19

Frictional force between solids and liquids.

Question 20

What is hookes law (equation)

Answer 20

Force applied = Stiffness constant x extension

Question 21

What is the limit of proportionality

Answer 21

Maximum extension or strain that an object can exhibit for which I still proportional to the load

The limit of proportionality is the is the point beyond which Hooke’s law is no longer true when stretching a material.

Question 22

What is Tension?

Answer 22

Force acting on a material that extends it

Question 23

What is extension?

Answer 23

Increase in size past the tension force

Question 24

What is the elastic limit?

Answer 24

Maximum extension or compression that a material can undergo and still return to its original form when force is removed

Question 25

What is hysteresis?

Answer 25

Where the extension under a certain load will be different depending on its history of past loads and extensions

Question 26

Equation of elastic strain?

Answer 26

E=0.5 x F x extension

Question 27

Work done of deforming material

Answer 27

extension x average force

Question 28

What does the area under underneath force-extension graph represent?

Answer 28

Work done

Question 29

What is stress?

Answer 29

A measure of force within a material but taking into account the coss sectional area

Question 30

What is the equation for stress?

Answer 30

Stress (Pa) or (Nm) = force / cross sectional area

Question 31

What is strain?

Answer 31

Strain is a measure of the extension of a material but taking into account the original length

Question 32

What is the equation for strain?

Answer 32

Strain = extension / original length

Question 33

What is young modulus?

Answer 33

Stress is partitional to strain when a material is deformed elastically.

The stiffness constant is called young modulus so young modulus is the stiffness of a material

Question 34

What is the equation for young modulus?

Answer 34

Stress / strain

Question 35

In a graph of forces applied to a spring vs extension what does the area underneath represent ?

Answer 35

Energy stored in the spring

Question 36

Explain why a long and thin copper wire Is used when measuring Young’s modulus

Answer 36

Small extension would mean it’s harder to measure accurately

Small extension means larger room for uncertainty

Stress= force/area so thin wires with smaller surface area gives larger stress without a huge force

Longer length means there can be a greater extension than if it was short. This is because less force is required for an extension of the wire

Smaller surface area means greater extension because less force is required for the extension