# Physics revision flashcards

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• Created by: Jess <3
• Created on: 15-01-13 14:32
Series Circuits
Current ( measured by an ammeter )= Same all way round. Current is the measure of the rate of flow of negatively charged electrons
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Parallel Circuits
Current= Splits and current going into a junction is the same as going out. Voltage = Same around circuit
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Resistance
Collision of electrons prevent electrons moving freely through a wire - this is the resistance. More frequent collisions= higher resistance
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Speed and Velocity
Speed= Measure of how fast or slow somethings moving. Velocity= speed in a given direction
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Graph of Motion
Curved slope= acceleration Constant slope= constant velocity Straight line = stationary
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Velocity Time Graphs
Zero Velocity= stationary Flat straight line= constant velocity Sloping straight line= acceleration/deceleration Area under graph= distance traveled ( area of triangle = half *base*height)
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Newtons first Law of motion
An object at rest stays at rest, or an object in motion stays in motion, with the same speed in the same direction unless acted upon by an unbalanced force
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Inertia
The mass of an object dictates how easy (or difficult) it is to change the motion of the object. Inertia is defined as the resistance of any object to change in its state of motion or rest
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Momentum
product of the mass and velocity of an object. Objects have a large momentum if they are very massive or moving at high velocity
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The forces and motion at take-off
At take off the mass (therefore the weight) of the rocket starts to decrease because it uses up fuel , so resultnt force starts to become bigger in the upwards direction , causing the rocket to lift off and accelerate
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Newtons second Law of motion
When an object accelerates it changes its velocity from one value to another. So when it accelerates it also changes momentum; the resultant force acting on an accelerating object is equal to the rate of change of momentum of the obect
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Opening a parachute
Increases air resistance on the descent module as the area in contact to air increases, causing the descent module to decelerate rapidly reducing its velocity to a slower velocity
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Kinetic Energy
Movement energy dependent on the mass and velocity of object
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Gravitational potential energy
If a ball was kicked up, all the KE would be converted to GPE. In distance kicks, only a proportion of KE is converted to GPE as some KE is used up kicking the ball forward.
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Newtons third Law
For every action force, there is an equal and opposite reaction force
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Newtons third Law - points to be understood
1) The two forces are in an interaction pair act on different objects 2) The two forces are equal in size, but opposite in direction 3) The two forces are always the same type e/g contact forces or gravitational forces
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Type of forces
Push,pull,tension,friction,thrust,upthrust, air resistance
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Total stopping distance
thinking distance (distance vehicle travels whilst driver sees the hazard thinks about braking then reacts) + braking distance ( distance vehicle moves while brakes are applied, during this time the vehicle is decelerating to 0 m/s)
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Thinking distance factors
-velocity of car - reaction time of driver( can be affected by alcohol, drugs, tiredness or drowsyness from medication) - distractions ( kids , mobile phone, sat nav, eating)
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Braking distance factors
- Velocity of car - mass of car - condition of the brakes - Tyre conditions - road surface conditions - Conditions of the weather ( ice / snow reduces friction )
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Traffic 'calming' methods
-cameras(white mark on roads enable police to see how far the driver has traveled in the time between the flashes also working out the velocity)-speed bumps(people slow down to risk damage to cars)-road width restrictions(1sidestops4oncomingtraffic)
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Crumple zones
Collapse gradually on impact - increases time of collision so reducing force on the occupants. It allows bonnet and engine to crumple in itself. Takes alot of KE out of the crash, deforming front end of car
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Safety cage
prevents crumple zone from impacting inwards towards the passengers and they now have side impact bars making the crumple zone strong against side impacts
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Seat belts
The stretchy material increases time of collision reducing the rate of change of momentum and therefore the force that acts on you. Some sense impact and tighten slightly to reduce effect of collision of head on steering wheel or windscreen
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Air Bags
Inflate automatically on impact. When head hits it, bag deflates slowly as the force pushes some gas out. increases time for head to slow down and stop so least force on head
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Alpha Beta and Gamma
forms of ionising radiation that can kill body tissue- the energy of the radiation can cause atoms in the cell to ionise, so mutating and killing them in the process
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Half Life
The time it takes for half the number of atoms in any sample to decay.(time taken for activity to half) For any one type of atom this is constant.
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Half life of isotopes
Isotopes with very long half lives remain radio active for a long time whereas isotopes with very short half lives only remain radioactive for fractions of seconds
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Geiger Counter
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Carbon Dating
The determination of the age of an organic object from the relative proportions of the carbon isotopes carbon-12 and carbon-14 in it.
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Working out date ( half life 5730 found in 1988)
From the graph, approximately 1/6 of a half-life has elapsed, so 5730/6 = 955 years Sample was produced in 1988 – 955 = 1033AD
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Alpha
two protons two neutrons identicle to a hlium nucleus. Penitrates sheet of paper. Very high ionising power
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Beta
an electron emitted from a nucleus when a neutron decays into a proton and electron. Penetrates few mm aluminium. Medium ionising power
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Gamma
Electromagnetic ray emitted from nucleus. Reduced penitration by several cm of lead. Low ionising power.
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Why is Gamma used to sterilise lots of things
Gamma kills harmful bacteria on medical scalpals, used becuase dosent become radioactive because highly penitrationg so can pass straight through the packaging and the products they are sterilising
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Nuclear fission
Using the breaking up of U-235 into two nuclei to produce heat energy. If the daughter nuclei are bombarded with slow moving neutrons , fission occurs producing slow moving neutrons etc ( chain reaction)
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Moderator
The fission of U-235 by neutrons requires the neutrons to be slow-moving – the moderator, usually water, is used to slow the neutrons down increasing the likelihood of fission events
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Controlling a reaction
Control rods, usually made of graphite or boron, absorb neutrons. Raising or lowering the control rods controls the rate of fission and hence the power output of the reactor. Incased in concrete to reduce risk of gamma penitrating into environment.
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Nuclear fusion
Nuclear fusion is the joining together of lighter nuclei to make heavier ones and during the process emitting large amounts of energy. Inside the Sun, hydrogen nuclei (protons) fuse together during the process of nuclear fusion
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What is needed for fusion
High temperatures and pressures are needed to ensure that enough protons get close enough for the process of nuclear fusion to occur.
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Controlling fusion
Nuclear fusion reactors produce huge numbers of high energy neutrons which need to be contained to prevent damage to the human operators.
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## Other cards in this set

### Card 2

#### Front

Current= Splits and current going into a junction is the same as going out. Voltage = Same around circuit

#### Back

Parallel Circuits

### Card 3

#### Front

Collision of electrons prevent electrons moving freely through a wire - this is the resistance. More frequent collisions= higher resistance

### Card 4

#### Front

Speed= Measure of how fast or slow somethings moving. Velocity= speed in a given direction

### Card 5

#### Front

Curved slope= acceleration Constant slope= constant velocity Straight line = stationary

#### Back

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5 star :)

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