# Mechanics & Materials

• Created by: Lucy
• Created on: 28-04-14 18:51
What do Scalar Quantities have?
Magnitude only
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What do Vector Quantities have?
Magnitude and Direction
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How do you find the Resultant of vectors that are acting in the same straight line?
If they're going in the same direction, just add them. If they're in opposite directions take one of them as negative and then add
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How do you find the Resultant of vectors that are perpendicular to each other?
Draw the vectors as adjacent sides of a rectangle. The resultant is the diagonal of the rectangle.
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What is Free Fall?
The motion of an object undergoing an acceleration of gravity
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What is the only force acting on an object in Free Fall?
Weight
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What does the gradient of a displacement-time graph tell you?
Velocity
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What does the gradient of a velocity-time graph tell you?
Acceleration
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What does the area under a speed-time graph tell you?
The distance travelled
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What is the definition of Mass?
The amount of matter in an object, measured in kg
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What is the definition of Weight?
The force experienced by a mass due to a gravitational field, measured in N
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What is the equation relating both Mass and Weight?
Weight=Mass x Gravitational Field
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What is the definition of Density?
The measure of the "compactness" of an object
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What is the equation for Density?
Density = Mass/Volume
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What is the Centre Of Gravity?
The single point on an object where you can consider its whole weight to act through
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What is a Free-Body Diagram?
Its a diagram which shows an object on its own with all of the forces that act on that object labelled on it
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What does it mean when an object is in equilibrium?
The object is not accelerating and all of the forces acting on it are balanced
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What does Newtons 1st Law state?
The velocity of an object will not change unless a resultant force acts upon it
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What does Newtons 2nd Law state?
Acceleration is proportional to the force applied. "Resultant Force=Mass x Acceleration"
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What does Newtons 3rd Law state?
Every force has an equal and opposite reaction force
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What is the definition of "Work"?
The amount of energy that transferred from one form to another when a force causes some sort of movement
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What is the definition of "Power"?
The rate of doing work. Power = Work Done/Time. Power=Fv
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What does the Principle Of Conservation Of Energy say?
Energy cannot be created or destroyed, it can only be transferred from one form to another.
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What are the two types of Potential Energy?
Gravitation Potential Energy & Elastic Potential Energy
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What is Gravitational Potential Energy?
The energy something gains if you lift it up
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What is Elastic Potential Energy?
Elastic stored energy. The energy you get when you stretch an object, eg an elastic band
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What does Hooke's Law state?
That extension is proportional to the force applied
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What is the equation for Hooke's Law?
F=ke. Where F is the force, k is a constant and e is the extension
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What is Elastic Deformation?
The material returns to its original shape/size once the force being applied has been removed
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What is Plastic Deformation?
The material is permanently stretched and does not return back to its original shape or size
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What is meant if the force is described as being Tensile?
The force has stretched the object/material
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What is meant if the force is described as being Compressed?
The force has squashed the object/material
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What is the equation for Stress?
Stress= Force/Cross-Sectional Area
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What is the equation for Strain?
Strain= Extension/Original Length
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What are the units of Stress?
Nm-2 or Pa
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What is the "Ultimate Tensile Stress"?
The maximum stress that the material can withstand
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What is the "Breaking Stress"?
This is when the atoms in the material separate completely and so the material breaks
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What is the equation to find the Young Modulus of an object?
E (Young Modulus)= Stress/Strain
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How do you find the Young Modulus of an Object?
Plot a graph of Stress against Strain. Calculate the gradient from the straight line part of the graph. The gradient is the Young Modulus
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What is the "Limit Of Proportionality"?
This is the point where the object stops obeying Hooke's Law
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What is the "Elastic Limit"?
This is the point where the object starts to behave plasticially
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What is the "Yield Point"?
The point where the material stretches without any extra load
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What are Fluid Elements?
Part of the fluid in which all of the particles are flowing in the same direction, at the same rate.
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Describe Laminar Flow
Is a flow pattern where all of the fluid elements flow in the same direction. This results in all of the flow lines are streamlines that run parallel to each other
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Describe Turbulent Flow
A flow pattern where the fluid elements get mixed up. The fluid moves in miniature whirlpools called eddy currents
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Define "stiff"
Materials that are hard to stretch
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Define "flexible"
Materials that are easy to stretch
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Define "elastic"
Materials that return back to their original shape/size after they've been stretched
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Define "plastic"
Materials that permenantly deform when they're stretched
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Define "ductile"
Materials that can be drawn out into wires but still keep their strength
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Define "malleable"
Materials who's shape can be changed easily but they may not keep their strength
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Define "tough"
Materials which are hard to break, and when they do break deforms plasticially
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Define "brittle"
Materials which break suddenly without deforming plasticially
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Define "viscosity"
A measure of how easily a fluid flows. The thicker a liquid the higher its viscosity.
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What is Contact Force?
The force of gravity pulling you towards the centre of the earth
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What does Pressure tell us?
How concentrated a force is. Pressure=Force/Area
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What is the Centre Of Mass?
The single point where we can take all of an objects mass to act
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What is Terminal Velocity?
It's the maximum possible speed something can travel at. There is no net force acting and its not accelerating. Air resistance and weight are balanced out.
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## Other cards in this set

### Card 2

#### Front

What do Vector Quantities have?

#### Back

Magnitude and Direction

### Card 3

#### Front

How do you find the Resultant of vectors that are acting in the same straight line?

### Card 4

#### Front

How do you find the Resultant of vectors that are perpendicular to each other?

### Card 5

#### Front

What is Free Fall?