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Flashcards in P2 b Deck (54):

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

Change in momentum


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