P2 b Flashcards
What affects your braking distance
Your thinking and braking distance
What affects your thinking time
Your reaction time and how fast your going the faster you go the more ground will be covered before reactions take place
What factors affect braking distance
How fast your going, the mass of the vehicle a heavier vehicle takes longer to stop. How good your brakes are and how good the grip of the tyres is .
What affects a tires grip
Road surface weather conditions and tyre conditions
How do you calculate an objects momentum
Mass x Velocity
What happens to momentum after an incident
The same momentum is present the total momentum after is the same as before
What happens when a force acts on an object
It causes a change in momentum
How can you calculate the force
Time
What does a larger force mean
A faster change of momentum
Why do cars have airbags and such?
To extend the time the change in momentum occurs over in order to reduce the force acting on the body
What are examples of safety mechanisms in cars
Crumple zones, these increase the time taken for the car to stop
Seat belts stretch slightly increasing the time for the wearer to stop
Air bags slow you down more gradually
What is work
It is when a force moves an object and energy is transferred this means work is done
What is power
Is the rate of doing work it is calculated by the work done divided by a given time
What is power measured in
Watts or joules 1 watt = 1 joule of energy transferred per second
Watts are the same as joules per second
What do all moving objects have
Kinetic energy
How to calculate kinetic energy
1/2 x mass x velocity squared
What is gravitational potential energy
It is the potential energy an object holds mainly affected by its height as that can vary
How do you calculate G.P.E
Mass x gravitational field strength x height
What is the principle of conservation of energy
Energy can never be created nor destroyed.
When an object falls the kinetic energy gained is equal to
The gravitational potential energy lost
What is a problem assuming that kinetic energy gained = gravitational potential energy lost
It doesn’t account for other factors such as heat or sound
What happens to unstable nuclei
They decay this is random
What are the three types of ionising radiation
Alpha, short range, weak penetrating
Beta, medium range, medium penetrating
Gamma, long range, highly penetrating
What does ionising radiation mean
They cause the ionising of atoms or loosing of an electron
How does alpha radiation ionise
It has a large positive charge when it passes close to an atom it pulls an negatively charged electron out of orbit
How does beta radiation ionise
It is negatively charged so pushes electrons out of orbit
How is gamma radiation ionising
The transfer energy to electrons if the electron gains enough energy it can break free
What are alpha particles
Helium nuclei
Big heavy slow moving positive charge. Paper stops it
What are beta particles
Electrons emitted from a nucleus
Fast and small negative charge, moderately ionising but stopped by aluminium .
What happens when a beta particle is emitted
A neutron turns into a proton in the nucleus
What is a gamma rays
Electromagnetic radiation weakly ionising only stopped by thick lead
What is nuclear fission
The splitting up of atoms
How to start a chain reaction
A slow moving neutron is fired at an isotope of uranium. Th neutron is absorbed by the nucleus it becomes unstable and causes it to split
How are chain reCtions controlled
Placed in a moderator to slow down the neutrons I.e water this creates a steady rate of nuclear fission. Control rods made of boron limit fission by absorbing excess neutrons
What is nuclear fusion
The joining of two smaller nuclei to make a larger one. This usually happens inside stars and requires extreme pressure and heat
Why doesn’t nuclear fusion happen at lower pressures and temperatures
Due to electrostatic repulsion of protons
Why is a fusion reactor hard to build
Most materials are vaporised at the temperature so you have to contain hot hydrogen in a magnetic field instead of physical container
What is background radiation
Low level radiation that around all the time
Where does background radiation come from
It comes from natural unstable isotopes radiation from space know as cosmic rays and radiation due to human activity I.e nuclear fallout
What is half life
The time taken for half the undeclared nuclei to decay
What is the radioactivity of an isotope measured in
Becquerel s 1Bq is 1 decay per second
How to measure half life from a graph
Measure the background radiation count first and subtract it from the isotope count. Then divide that by two and find this point on the graph across and down to time
What are some uses of radioactive decay
Smoke detectors
Sterilisation of food
Trackers and thickness gauges
Treating cancer
How is alpha radiation used in smoke debtors
A weak source of alpha is placed in a smoke detector close to two electrodes. The source causes ionisation and a current flows. If there is a fire then the smoke will absorb the radiation causing the current to stop and the alarm to trigger
How is food sterilised
Exposing it to high doses of gamma rays will kill all microbes. This is called irradiation this can be used for medical equipment too
How does a thickness gauge work
Beta radiation is used in thickness control. You fire beta at the object and place a detector on the other. When the amount of beta detected changes the thickness must of changed. This source must half a long half life.
What can ionising radiation cause
Tissue damage and cell mutation
What do lower doses of radiation do
Minor damage without killing the cell leading to mutant cells which divide uncontrollably
What effect do higher doses of radiation have
They tend to kill cells this causes radiation sickness
How can you minimise exposure to radioactive isotopes in the lab
Never allow skin contact and handle with tongs, keep the source at arms length, keep it pointing away and don’t look at it. But the source in a lead box.
What is a problem with nuclear fission reactor s
They create radioactive waste products, they can’t be recycled and usually have very long half lives.
How do plants deal with radioactive waste
By vitrification , thy melt the waste with other materials to form a type of glass it is then sealed in steel canisters and buried . The general idea is to hide it in a place where the materials around it absorb the radioactive waste before it reaches the surface
What are the negatives of nuclear power
Public perception is negative they see it as dangerous. Some believe nuclear waste can never be disposed of safely there is always a risk of leaks. Nuclear power carries the risk of major incidents such as Chernobyl . The building of the plant is extremely expensive and dismantling safely takes decades
What are the pros of nuclear power
It is actually a pretty safe way of generating electricity . It is reliable and reduces the need for fossil fuels. It doesn’t real ease greenhouse gases like fossil fuels such as carbon dioxide . Huge amounts of energy can be generated from a relatively small amount of nuclear material . Fuel is pretty cheap and readily available
