Physics but Shorter Flashcards
Define inertia
How hard it is to change the motion of an object
State Newton’s First Law
A body will remain at rest, or continue to move with a constant velocity unless acted upon by an external (resultant) force
Resultant force definition
The total force acting upon an object
Newton’s Second Law
Resultant force = mass x acceleration (this means that acceleration is directly proportional to resultant force)
Define weight and mass
Weight - the measure of how large the force of gravity is on an object (N)
Mass - the measure of how much matter an object has (kg)
What is Newton’s Third Law
If object A exerts a force on object B, object B also exerts an equal and opposite force on object A.
What kind of energy is kinetic energy
Movement energy - faster objects have more kinetic energy
How is energy taken away from KE and GPE
It becomes friction (work done)
State Hooke’s Law
The extension of a material is directly proportional to the force applied
How is work done represented
As the area under a force extension graph
What are the ways vehicles lose energy and what are the ways to improve them
- Aerodynamic losses: more streamlined
- Rolling resistance: correctly inflated tyres from right material
- Idling losses: stop-start systems turn off the engine in traffic
- Inertial losses: lighter car (carbon fibre, not heavy metal)
Car safety features
- Seat belt
- Crumple zone
- Air bag
- Side-impact bars (strong bars inside car doors)
- Passenger cell (a rigid cage around passengers)
What do car safety features do
They slow the passengers down as gradually as possible which means the force also decreases - they also increase the distance over which energy is transferred (force=work done/distance)
Momentum fact file
- Momentum is the amount of motion an object has
- Measured in kgm/s
- Total momentum before interaction = total momentum after interaction
Two words relating to kinetic energy in car crashes
Elastic collision and inelastic collision (inelastic means kinetic energy is lost)
What accelaration is given by gravity
10m/s squared, so if an object is thrown up this becomes -10
Moment fact file
- A moment is the turning effect of a force
- Moment = force x distance to the pivot
- The sum of the clockwise moments about a point is equal to the sum of the anticlockwise moments about the same point
- When the moments of each side are balanced they are in equilibrium
What is an astronomical unit
The mean distance from the earth to the sun
Give the main stages of the life cycle of a star
- Protostar
- Main sequence
- Red giant
- White dwarf
OR - Red supergiant
- Supernova
- Black hole / neutron star
What creates outwards pressure in stars
Gas and radiation pressure
Two types of evidence for the big bang
- Cosmological red shift
- Cosmic microwave background radiation
Key terms for cosmological red shift
- Continuous spectra: a full rainbow of light
- Absorption spectra: a continuous spectra that’s been blocked
Why are the waves in CMBR microwaves
Because they’ve stretched from the original gamma rays
How does a galaxy’s distance from us correlate with red shift?
The further away it is the greater the redshift
Define isotope
Atoms of the same element which have the same number of protons but a different number of neutrons
Define ionising
When radiation interacts with cells and damages DNA (cancer)
Alpha fact file
- Its symbol is below
- It is a helium nucleus
- It can be stopped by a thin sheet of paper or a few cm of air
- It’s very damaging to the body
Beta fact file
- Its symbol is below
- It is a fast moving and high energy electron
- Can be stopped by a few mm or aluminium or 1m air
Gamma fact file
- Only stopped by several cm of lead or very thick concrete, so passes easily through the body
What is the process for storing nuclear waste
- It’s first cooled in large water tanks
- It’s turned into a type of glass so it can’t flow
- It’s placed inside steel drums and sealed in concrete
- It’s buried deep underground
Radon gas factfile
- It emits alpha
- It goes from uranium to radium, radon and polonium
- Because radon is a gas it can be breathed in
- Cornwall has the highest concentration
What is activity and what is it measured in
It’s the measure of decays per second and measured in becquerels - also known as the count rate
What happens in a nuclear fission power station
- Uranium -235 in fuel rods absorbs a slow moving neutron which makes it unstable
- The uranium decays and splits into two smaller nuclei, and a large amount of energy is released
- These neutrons cause more atoms to undergo fission
- This is a chain reaction
Name features used in the reactor to stop out of control chain reactions
- The moderator slows down neutrons (this is either water or graphite rods)
- Boron control rods are dropped into the reactor to slow the reaction - they absorb extra neutrons
- The reactor is surrounded by concrete
- Water acts as a coolant
What would nuclear fusion involve and where would we get the fuel
Two isotopes of hydrogen making helium, taken from sea water
Which laboratory is most advanced for fusion and what does it involve
The JET laboratory which has a doughnut shaped reactor where the particles are accelerated into each other
