Physics Unit 2

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  • Created by: Emily
  • Created on: 16-05-13 16:05
What is the difference between speed and velocity?
Speed is how fast you are going, whereas velocity must also have a direction specified as well as the speed
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How do you calculate speed?
Speed = distance / time
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What is acceleration?
How quickly the velocity is changing, this can be a change in speed, a change in direction or both
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What is the formula for acceleration?
Acceleration = change in velocity / speed
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If a line on a velocity-time graph is horizontal, what does this mean?
There is a steady or constant speed
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Gravitational force is the force of attraction between all masses, true or false?
True
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Define the difference between mass and weight
Mass is the amount of 'stuff' in an object (measured in kg), weight is the centre of the Earth (measured in N)
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The formula to find weight is weight = mass x gravitational field strength, how would you work out the mass?
Mass = weight / gravitational field strength
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What is meant by a 'resultant force'?
The overall force acting upon an object, this tells us whether the object is accelerating decelerating or stationary
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If there is a resultant force acting upon an object what will happen?
There will be a change in the object's velocity
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What would the resultant force have to be for an object to be stationary?
Zero
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If there is no resultant force on a moving object, what will happen?
It will carry on moving at the same velocity - the same speed and direction
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What causes an object to accelerate or decelerate?
Having a non-zero resultant force, meaning that one of the forces on the object is bigger or smaller than the rest - it can take five forms, starting, stopping, speeding up, slowing down and changing direction
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When two objects interact, are the forces they exert on each other equal or not?
Yes, the forces exerted on each other are equal and opposite
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Which direction does friction act in?
The opposite direction to movement
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When do you get friction?
When two surfaces are in contact and at least one is moving, or when an object passes through a fluid
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What is terminal velocity?
The point at which an objects frictional force is equal to its accelerating force, so its reached it maximum speed and is moving at a contant rate
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Identify the two main things affecting someones stopping distance
Their thinking distance and their stopping distance
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What could affect someones breaking distance?
How fast they're going / how good the breaks are / how good the tyres are / how good the grip is
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Finish this statement: when a force moves an object through a distance energy is transferred and...
Work is done
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What is the equation for finding out the 'work done'?
Work done = force x distance
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What is the gravitational potential energy?
The energy that an object has because of its vertical position in a gravitational field
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What is the symbol formula for finding out kinetic energy?
Ek = 1/2 x m x v(squared)
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What happens to the potential energy when something falls?
The potential energy is converted into kinetic energy (kinetic energy gained = potential energy lost)
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What is the equation that realates the force of a spring and its extension?
F = k x e
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What happens to an elastic object that is streched past its limit of proportionality?
The material will become permanently stretched, and when the force is removed the material will no longer be at its starting length
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Name the 2 things that affect the momentum of an object
The mass and the velocity of the object
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What is the formula for momentum?
Momentum = mass x velocity
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How do seat belts and crumple zones in a car help prevet serious injury in a crash?
Seat belts stretch to increase the time taken for the wearer to stop, reducing the forces acting upon their chest and absorbing some of their kinetic energy. Crumple zones convert the cars kinetic energy into other forms, and increase the impact time
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What causes a build up of static electricity?
Static electricity is caused from friction of two insulating materials being rubbed against each other
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Which particles move when static electricity builds up?
Positive and negative electrons
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Which types of charges will repel eachother?
Like charges - negative and negative or positive and positive
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If the resistance across a component is greater, is the current flowing throught the component smaller or larger?
The greater the resistance, the smaller the current will be
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What is resistance, and what units is it measure in?
Anything in the circuit which slowes the flow down, measured in ohms
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What formula relates work done, potential difference and charge?
Potential difference = work done / charge
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What does a voltmeter measure and where in a circuit can it be placed?
It measures the potential difference in volts acrodd the component, so must be placed in parallel around the component
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What is potential differnce?
The driving force that pushes the current around a circuit
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If the temperature of the filament in a filament lamp increases, what happens to the resistance?
The resistance will increase too
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True or false, a diode is used to ensure current is free to flow in any direction around a circuit
False, a doide ensures that the current will only flow in one direction
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In terms of ions and electrons, how does the resistance of a component change with changes in temperature?
As temperature incerases, the ions in the conductor recieve more energy and start to vibrate more, so becasue the ions are moving around more this makes it more difficult for the current to flow through the resistor, so the resistance increases
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What is a light emitting diode? Give an example of how they're used
A light emitting diode emits light when a current flows through in a forward direction, indicating the presence of a current in a circuit. They are used in appliances such as TV's to show when they're on / numbers on digital clocks / remote controls
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What happens to the resistance of a thermistor in hot and cold conditions?
In hot conditions resistance drops, and in cold condition resistance goes up
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What is an LDR (light-dependant resistor)?
A resistor dependant on the intensity of light, in bright light resistance falls, in dark like resistance is highest
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In a series circuit, is the current the same through the whole circuit?
Yes
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How do you know that a car uses parallel circuits rather than a series circuit?
You can tell because everything can be turned on and off seperatly and everything always gets full voltage from the battery
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Is mains elecricity AC or DC? What does this mean?
It's AC meaning that the currnet is constantly changing direction
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What are the 3 wires in a core cable?
Live wire, neutral wire and earth wire
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What is the purpose of having an earth wire?
The earth wire protects the wiring, and is used for safety the prevent fire and shocks along with the fuse
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In a plug, why are the case, cable grip and cable insulation made from rubber or plastic?
Because they are very good insulators and also flexible too
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Give 2 advantages of circuit breakers
Protect the circuit from damage if too much current flows through / can be reset easily by flicking a switch / do not have to be replaced one the circuit is broken
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Explain how the experiments of Rutherford and Marsdon led to the nuclear modal of the atom
They fired a beam of alpha particles at thin gold foil, results showed most particles went strainght through, with the odd one being refracted back. Making them realise most of the mass of the atom was concerntrated at the centre in a tiny nucleus
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What did Rutherford and Marsdon realise most of the atom was?
Empty space
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What is an isotope?
Atoms with the same number of protons but a different number of neutrons
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Give 3 examples of where background radiation may come from
Radioactivity of naturally occuring unstable isotopes / radiation from space (cosmic rays) / radiation due to man-made sources (nucleary waste)
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What is an alpha particle?
A particle made from two neutrons and two protons (same as a helium NUCLEUS, not helium atom) with a large mass and a charge of +1
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What is a beta particle?
An electron with virtually no mass and a charge of -1
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Alpha and beta particles are deflected by electric and magnetic fields, why?
The particles will be deflected in a magnetic or electric field and due to their opposit charges, they're deflected in opposite directions
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What is 'half-life'?
The average time it takes for the number of nuclei in a radioactive isotope sample to halve
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Give 4 uses of radiation
Smoke detectors / tracers in medicine / radiotherapy / steralisation
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Outside the body which sources of radiation are the most dangerous?
Beta and gamma particles because they can get penetrate the skin and get inside delicate organs
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Inside the body which sources of radiation are the most dangerous?
Alpha particles becasue they will do all of their damage in a very localised area
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What is nuclear fission?
It is the process of splitting up large atomic nuclei in order to release energy in the form of heat
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What is nuclear fusion?
The process whereby light nuclei
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Describe the steps that lead to the initial formation of a star
Gravity forces dust and gas to spiral together to form a protostar, this gravitational energy is converted to heat energy and eventually hydrogen nuclei undergo nuclear fusion to form helium nuclei giving out masses of heat and light. A star is born
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Why could our sun never form a balck hole?
Because our sun is not a massive main sequence star so it could only form into a red giant, then when it becomes unstable it would eject its outer layer of dust and gas as a planetary nebula and leave a white dwarf, which cools into a black dwaf
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Other cards in this set

Card 2

Front

How do you calculate speed?

Back

Speed = distance / time

Card 3

Front

What is acceleration?

Back

Preview of the front of card 3

Card 4

Front

What is the formula for acceleration?

Back

Preview of the front of card 4

Card 5

Front

If a line on a velocity-time graph is horizontal, what does this mean?

Back

Preview of the front of card 5
View more cards

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