Chapter 4 Materials (4.1) Flashcards
Density formula?
Density = mass / volume
What is upthrust?
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
Equation for mass of fluid displaced?
Volume of object x density of fluid
When will on object float?
When liquid displaced = weight of object
What is a hydrometer?
A piece of equipment that is used to determine the density of a fluid.
How does a hydrometer work?
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.
How can a hydrometer determine how alcoholic a drink is?
The more alcohol content the lower the density.
What is laminar flow?
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
What is streamlining?
The line of laminar flow are called streamlines. Streamlines are lines of laminar flow in which the velocity is constant over time
What is turbulent flow?
Where fluid velocity in a particular place changes over time, often in an unpredictable manner
Why do you find it harder to walk in water than through air?
The friction acting against you in water is greater than it is in air (Viscosity of the water)
If a liquid is extremely viscous. Is it faster or slower than a less viscous liquid?
Slower
What is viscosity?
Viscosity is essentially how resistant a fluid is to flowing.
What is the coefficient of viscosity?
Value given to a fluid to indicate how much it will resist flow
What is terminal velocity?
When an object falling reaches equilibrium between the weight and the sum of up thrust and drag
When is an object at terminal velocity ?
When it is no longer accelerating but instead falling at a constant velocity
What is Stokes law?
F=6(Pie)(radius of sphere)(n (coefficient of viscosity in fluid))(terminal velocity)
Equation combining stokes law with weight?
Weight = Weight of fluid displace + Stokes Law
What is viscous drag?
Frictional force between solids and liquids.
What is hookes law (equation)
Force applied = Stiffness constant x extension
What is the limit of proportionality
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.
What is Tension?
Force acting on a material that extends it
What is extension?
Increase in size past the tension force
What is the elastic limit?
Maximum extension or compression that a material can undergo and still return to its original form when force is removed
What is hysteresis?
Where the extension under a certain load will be different depending on its history of past loads and extensions
Equation of elastic strain?
E=0.5 x F x extension
Work done of deforming material
extension x average force
What does the area under underneath force-extension graph represent?
Work done
What is stress?
A measure of force within a material but taking into account the coss sectional area
What is the equation for stress?
Stress (Pa) or (Nm) = force / cross sectional area
What is strain?
Strain is a measure of the extension of a material but taking into account the original length
What is the equation for strain?
Strain = extension / original length
What is young modulus?
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
What is the equation for young modulus?
Stress / strain
In a graph of forces applied to a spring vs extension what does the area underneath represent ?
Energy stored in the spring
Explain why a long and thin copper wire Is used when measuring Young’s modulus
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
