Physics 1 Flashcards
What is an atom?
- Fundamental building blocks of matter
- Smallest particles into which an element can be reduced to
- contains protons, neutrons and electrons
Which sub atomic particles are responsible for the majority of mass in an atom?
- Proton
- Neutron
Which sub atomic particles can be found in the nucleus of an atom?
- Proton
- Neutron
Define an ‘element’ in terms of the kind of atoms it contains?
An element is a pure substance that consists only one type of atom
Elec charge in the following?
Neutrons - Zero / neutral
Protons - Positive
Electrons - Negative
Define the term ‘mixture’
A substance that consists of 2 or more different substances not chemically bonded and not fixed to one another in proportion
Define the term ‘molecule’
A molecule occurs when 2 or more atoms are chemically bonded together
Define the term ‘compound’
A substance consisting of 2 or more chemically bonded and fixed ratio chemicals
Describe the states of matter
- Solid
- Liquid
- Gas
- Plasma
Explain how atoms can be electrically neutral?
A standard atom will have the same number of protons and electrons. The equal number of +ve and -ve charges act to cancel each other out - therefore becoming zero elec charge
How is a solid characterised?
- Molecules are close together
- Have definite volume and shape
- Incompressible
How are liquids characterised?
- Molecules are further apart (than solids)
- Molecules do not maintain regular pattern
- Easily move into shapes
- Have definite volume
- Will flow to the lowest possible position, due to gravity
- Are slightly compressed
- Conform to shape of container that are placed in
How is a gas characterised?
- Added more heat makes the particles move faster
- Molecules are much further apart (than liquids and solids)
- They space themselves out to fit whatever space they are put into
- Does not hold a fixed shape
What is the process called when changing from solid to liquid?
Melting
What is the process called when changing from liquid to gas?
Evaporation
What is the process called when changing from a gas to liquid?
Condensation
What is the process called when changing from liquid to solid?
Freezing
What is the process called when changing from liquids to gas?
Vaporisation or evaporation
Define density?
Density is defined as the amount of space a substance takes up compared to its mass
Define compressability?
Compressibility is defined as the change in volume for applied pressure
Define surface area?
The property of the surface of a liquid that allows it to resist an external force, due to the cohesive nature of its molecules
Define specific gravity
Density of a substance compared to the density of a substance as a known reference, measures as a ratio therefore no units
How do you calculate the specific gravity of a gas?
Ratio of the density of the substance compared to NTP air
What is the definition of elasticity
The amount a substance will change its shape compared to how much force is applied
Difference between scalar and vector?
Vector - requires direction as well as distance and time
Scalar - only requires distance and time
What are some examples of scalar quantities?
- Speed
- Distance
- Time
- Temperature
- Mass
What are some examples of vector quantities?
- Displacement
- Velocity
- Acceleration
- Force
- Weight
- Momentum
How do you add vectors?
Joining the tail of the first arrow with the arrow of the second
Newtons first law?
“A body at rest tends to remain at rest, a body in motion tends to remain in motion - unless an outside force acts upon it”
- Refers to inertia
One word used to explain Newton’s first law?
Inertia
Newton’s second law?
“The acceleration of a body is directly proportional to the force causing it, and inversely proportional to the mass of the body”
Equation for Newtons second law?
Force = mass x acceleration
Newton’s third law?
“For every action there is an equal and opposite reaction”
What does inertia cause mass to resist?
Directional change
Linear / translational motion - where does the force have to act from?
Centre of mass
How do you get rotational motion?
Circular motion of an object about a FIXED AXIS
What relationship does rotational motion depend on?
Between the angle of rotation and angle of velocity
Unit used for force?
Newton metres (N)
What happens to a stationary object when the force is applied to it?
Acceleration
Difference between mass and weight?
Mass - measure of amount of matter it contains
Weight - Force exerted on a body by the gravitational force of earth
What happens to a moving force when a force is applied in the opposite direction?
Deceleration
Defining properties of mass?
- Amount of material in body
- Measured by comparison of known mass
- Constant everywhere
Defining properties of weight?
- Force
- Measured using spring balance
- Vary considerably depending on where the body is related to other larger masses
Formula for weight?
Weight = mass x gravity
What is the magnitude of acceleration due to gravity?
9.8MS
Do objects always accelerate at 9.8ms squared in a uniformed gravitational field?
- Air resistance plays a role in this, the acceleration of gravity will not be realised due to drag and friction
Ways to increase an objects stability?
- Lower centre of gravity
- Widen base
How is centre of gravity determined in an aircraft?
Datum
What is normal reaction force?
Force moving upwards to resist gravity
When an object is stationary on a bench, what is the magnitude and direction of the normal reaction force?
- Upwards
- Equal to the mass of the object
3 types of friction?
- Static
- Dynamic / kinetic
- Rolling
What is the equation for the co-efficient of friction?
Resistive friction / Normal reaction force
What determines the change in resistance forces in the coefficient of friction?
Nature of surface (increased and decreased friction)
Once static friction is overcome, in order to maintain constant velocity, will I need to increase or decrease my applied force?
Decrease - less effort is required
If resistive force decreases, what happens to the coefficient of friction?
Decreases in proportion
Alternative name for moment?
Torque
Alternative name for torque?
A moment
Qualities that determine the amount of torque applied to an object?
- Force applied to the moment arm
- Moment arm distance
- Angle between the force and the moment arm
In order to maximise torque, what angle should this be applied from?
90 degrees or perpendicular
What is couple force?
Pair of forces (equal and opposite)
What is centripetal force?
- Uniformed circular motion
- Inward seeking
- Actual force
Apparent force that is opposite to centripetal force is?
- Centrifugal force
- Caused by inertia
- Apparent force
If an object is more dense than the fluid it is in, will it sink or float?
Sink
Define momentum
Mass of an object is multiplied by its velocity
Force that causes objects to sink or float?
Buoyancy
Define conservational momentum
Initial momentum = final momentum
What is required to change the momentum of an object?
External force pushing in the opposite direction
How do you reduce the impulse force on an object during collision?
- Reduce acceleration
- Increase time
Define impulse
The actual change in momentum
Which has a higher impulse? Elastic or inelastic?
Elastic
What is work?
A force acting on a body, moves the body
Unit for work?
- Joules (J)
- Newton meters (N)
How do you calculate work?
Work done = F x S x Cos
How is a joule defined?
1 joule = 1 Newton meter
Difference between kinetic and potential energy?
Kinetic - Motion
Potential - Stored
What is heat?
Transfer of energy through temperature
How is heat transferred?
Flows from higher to lower temperatures
What is thermal energy?
- Responsible for the speed that particles move with
Slower - They are closer together
Faster - Further apart
Why is it impossible for a machine / process to be 100% efficient?
There will always be waste due to heat, light, sound, friction etc
Formula for efficiency?
Energy out / Energy in x 100
Define mechanical advantage?
Ratio of the amount of force required compared to the force produced at the load
Formula for mechanical advantage?
Load force / Effort force
Define Velocity?
Ratio of distance through which the input part of the machine moves compared to the distance that the output part moves at the same time
Formula for velocity ratio
Distance moved by effort / distance moved by load
Define elasticity?
Ability to bound back into its original shape and dimension
Define stress?
The force that resists the deformation of an object
Define strain?
- Response an object has to the applied force
- Measured by the degree of deformation
Define torsion?
Twist reaction
Define tension?
- Tensile force
- Linear forces pulling outwards from the object
- Stretching
Define bending?
Compression and tensile stress forces
What is compression?
Ability for a substance to being forced into a lesser space
Define shear force?
Opposing forces are applied to each side of the object
Phase of matter that is incompressible?
Solid
Define incompressible?
Resists the object from being able to be crushed
Define specific gravity?
Include, reference substance for solids / liquids as well as gases
A measure of how the density of one substance is compared to another substance
Solids and liquids - Water at 4 degrees
Gas - NTP Air at 20 degrees
Formula for linear velocity?
Displacement / Time
Spinning part on a gyroscpe?
Rotor
Rigidity of a gyroscope?
Factors that affects the rigidity?
Resist any forces applied to it to change the direction
Factors:
- Mass of rotor
- Speed of rotation
- Distance that the mass acts from the centre
Factors that increase the rate of gyroscope precision?
- Strength and direction of the applied force
- Inertia of the rotor
- Angular velocity
How do you reduce the viscosity of a substance?
Heat it
Difference between laminar and turbulent flow?
Laminar - steady
Turbulent - Particles are moving at different speeds, bouncing off each other and colliding creating turbulence
What is the unit of measure for specific gravity?
It does not have one - it is a ratio
Purpose of streamlining aircrafts?
Reduce turbulence
Principles of streamlining a sonic aircraft?
- Forward part to be rounded
- Body to gradually curve back from the midsection
- To tapper off at the rear
Define pressure?
Continuous force exerted on or against an object by something contact it
How does pressure change with depth?
Increases
What tool is used to measure pressure in the atmosphere?
Barometer
Principle relied on for hydraulics? and what is it?
Pascals principle:
When a force is applied, any increase in pressure on a confined liquid was transmitted equally and undiminished to all parts of the container
How is lift created with the wings on an aircraft?
An aircraft wing, called an aerofoil is shaped so that the air has to travel further and faster over the top of the wing - therefore accelerating the air on the upper surface and reducing the static pressure - creating lift
How does venturi work?
- Narrow pipe
- Energy is unchanged
What causes liquid to be drawn into the venturi nozzle?
Suction point
Define power? and SI unit for power?
The rate at which energy is transferred from one form to another
SI unit - Watts
Formula for power?
Work done / time
Ratio for density?
Mass / Volume
How does a barometer work?
- Mercury
- open and closed end
- atmospheric pressure pushes down on the mercury and it rises in the tube
Torque wrench setting formula?
Desired torque x length / length + effective length
Law of conservation of energy?
Energy cannot be distroyed or created - only changed into different forms
Define speed?
Ratio of distance and time
Formula for speed?
Distance / time
Define acceleration?
Rate at which velocity changes in a given time
Define compresibility?
Ability of a substance to be forced into a lesser space
What is uniform acceleration?
Acceleration where the velocity changes at a constant rate
Are electrostatic forces exerted more for a solid or liquid?
Solid
2 types of molecules?
Compound and elemental
Compound - different types of atoms mixed - chemically bonded and fixed
Elemental - one type of atoms - pure - chemically bonded and fixed
What is a mixture?
Not chemically bonded and no fixed ratio
What is matter?
- Everything / all things physical in the universe
- Elements, molecules, compounds
Properties of plasma?
Move more freely
How is it possible to move between different states of matter?
Thermal energy
Where are the particles found in an atom?
Centre - Nucleus - protons and neutrons - contribute to the majority of the mass
Outer orbit - Electrons - very little mass
Periodic table?
- Elements in their purest form
- Metals, metalloids and non metals
In terms of properties of materials, define the following:
- Elasticity
- Hardness
- Conductivity
- Elasticity - Allows the material to deform and still remain / return to its original shape
- Hardness - Ability to resist indentation
- Conductivity - Permits the transfer of electrical charge or heat through its mass
