Unit 1 - Our Dinamic Universe Flashcards
How do you calculate
“Absolute Random Uncertainty”
(Largest Value - Smallest Value) / Number of Values
What is the accuracy of a analogue scale ?
Can be read to an accuracy of HALF the smallest scale division
What is the accuracy of a Digital scale ?
Can be read to an accuracy EQUAL to the smallest scale division
How do you combine uncertainties ?
- Calculate any random uncertainty
- Calculate the percentage uncertainty in all quantities
- Find the percentage uncertainty with the highest value, I.e. Worst uncertainty
- Calculate the absolute uncertainty in the result using the worst uncertainty chosen in 3.
What is a projectile ?
“A projectile is an object which travels with both horizontal and vertical components under the influence of Gravity”
What calculation would you do for each Horizontal and Vertical components of a projectile ?
Horizontal -> Speed = Distance x Time
Vertical -> U.V.A.S.T
V.U.A.S.T
What are the 3 graphs of projectiles that are in higher ?
Displacement / Time
Velocity / Time
Acceleration / Time
Which one of Newtons laws has an equation and what is the law ?
Newton II
F = ma
“If a mass is acted upon by an unbalanced force it will cause it to accelerate
What does a force of 1N cause on a mass of 1kg ?
A force of 1N can cause a mass of 1kg to accelerate at 1m/s
What is “Terminal Velocity” ?
Terminal Velocity is the maximum velocity you can travel while “falling”
Skydiving:
When you are in free fall, you will begin to accelerate as your weight is great than the air resistance acting against you, however eventually the air resistance will be equal to your weight, so you won’t accelerate anymore as the forces acting on you are balanced
What is “Apparent Weight” ?
“Apparent Weight”
Is the reading on (e.g. Scales) when there is an upwards force acting on you
If there is an upwards force greater than your weight, your apparent weight will be greater than your weight,
if the upwards force is less than your weight, your apparent weight will be less than your weight
How do you calculate “Weight Down a slope”
Competent acting parallel to the slope -> Mg x Sinx
Components acting perpendicular to the slope -> Mg x Cosx
What is momentum ?
Momentum is the product of
mass x Velocity
What is the Law of Conservation of Linear Momentum ?
The momentum before a Collision is Equal to the momentum after
In the Absence of any External Forces
What happens to kinetic Energy if there is an Elastic Collision ?
When there is an Elastic Collision, kinetic energy is conserved
What happens to Kinetic energy when a collision is Inelastic ?
When a Collision is Inelastic, Kinetic Energy is not conserved, lost.
During an Explosion, Kinetic Energy is gained.
What is Impulse ?
Impulse is equal to the change in an objects momentum
How would you calculate impulse (I.e. change in Momentum) ?
- Ft = Mv - Mu
2. Area under a Ft graph(A=1/2 bh)
What does Newtons Law of Gravitation state ?
“The Gravitational attraction between 2 objects is directly proportional to the mass of each object and is inversely proportional to the square of their distance apart”
What is the formula for Newtons Law of Gravitation ?
F = G x (mass1) x (mass2)
———————-
distance^2
“Big G” x both mass of each object,
divided by the distance squared
What is ‘Time Dilation” ?
Time Dilation is:
When an observer observes an event where an object is travelling close to the speed of light in their own reference frame either moving relative to the event or stationary and there is a difference of elapsed time between both frames of reference.
What is “Length Contraction?”
Length Contraction is:
When an observer observes an object travelling close to the speed of light in their own reference frame and measures a decrease in length of an object
What is the Doppler Effect ?
The Doppler Effect artists from a source of waves having a velocity relative to the observer
How do you know which frequency equation to use when calculating observed frequency ?
When the object is moving away from an observer we use ( V + Vs )
When the object is moving towards an observer we use ( V - Vs )
What is “Galactic Redshift” ?
Galactic Redshift is similar to the Doppler effect however with Light
Using Wavelength -> It tells us if objects are moving towards us or moving away from us
What is it called when an object (I.e a Galaxy) moves away from an observer (I.e. Earth)
Redshift
Note: If an object is Redshifted then the wavelength has increased
What is it called when an object (I.e. A star) moves towards an observer (I.e. Earth)
Blueshift
Note: When an object has Blueshifted the wavelength has decrease
What is the symbol for redshift ?
Z
What are the units for Redshift?
No Units
What does “Hubbles Constant” show us ?
Hubbles Constant shows is that the vast majority of galaxies are moving away from us
What can we derive from “Hubbles Constant” ?
The universe is constantly expanding
What is a “Black Body”
A “Black Body” is an object which is a perfect absorber AND a perfect emitter of radiation
What wavelengths of radiation does a “Black Body” emit ?
A Black Body emits ALL wavelengths of radiation
What evidence to we have for “The Big Bang” ?
- Cosmic BackGround Radiation
- RedShift
- Point of Singluarity
What are “Random Uncertainties” caused by ?
When an experiment is repeated many times and results are not identical
What are “Scale Reading” errors caused by ?
Due to the the precision on the instruments and measuring equipment used
What are “Systematic Errors” caused by ?
Due to mistakes in experimental design or measurement techniques
What are the 2 forms uncertainties can take ?
Absolute Uncertainty
Percentage Uncertainty
How do you calculate the percentage uncertainty?
Uncertainty
————- X 100
Value
What is Newton I ?
“An object at test or travelling at a constant speed will continue to do so unless acted upon by an unbalanced force”
What is the Unit for Force ?
Newtons (N)
What is the Unit for Acceleration ?
M/s^2
“Meters per second, per second”
Is weight a scalar or a vector ?
Since force is involved weight is a Vector
What is the Unit for Momentum ?
Kg ms^-1
“Kg meters per second”
What is the Unit for Impulse ?
Ns
“Newton Seconds”
Is impulse a Vector or a Scalar ?
Since Force is involved Impulse is a Vector
What is the value of the Universal Constant of Gravitation ?
G = 6.67 x10^-11
What are the Units for the Universal Constant of Gravitation ?
- Nm^2 Kg^-2
Or
- m^3 Kg-1 s^-2
What are Einsteins 2 postulates ?
- The laws of physics are the same for all observers in all reference frames
- Light always travels at the same speed in a vacuum regardless of reference frames