Term
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Definition
the steeper the line the greater the speed
Speed = distance / time
measured in m/sec |
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Term
| velocity and acceleration |
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Definition
velocity is speed in a certain direction
eg 30 m/s south
acceleration = change in velocity/time
Acceleration is the change in velocity per second.
*A body travelling at a constant speed is accelerating if it is changes direction
Acceleration measured in m/s squared |
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Definition
*slope represents acceleration so steeper the slope the greater the acceleration
* if slope coming down (negative gradient) this means deceleration
* area under graph is distance travelled |
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Term
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Definition
two objects that interact exert forces.
*force is measured in Newtons
*if resultant force is zero the object will carry on moving at constant speed and direction |
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Definition
| object will accelerate if force in same direction and decelerate if in opposite direction |
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Term
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Definition
| force = mass x acceleration |
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Term
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Definition
| thinking distance + braking distance |
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Term
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Definition
*weight is force due to gravity
objects free fall at 10m/s squared
* Weight = mass x 10
*objects falling in fluid reach terminal velocity(a constant velocity) |
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Term
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Definition
work done = force x distance moved
*measured in joules
*work is done whenever an object moves |
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Term
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Definition
energy of movement
*depends on mass and speed
kinetic energy= 1/2 mass x speed squared |
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Term
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Definition
all moving objects have momentum
momentum = mass x velocity
measured in kilogram metre/sec (kg m/s)
*whenever objects interact no momentum is lost (momentum is conserved) as long as no other external forces are acting |
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Term
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Definition
in an explosion (eg gun being fired) the objects move in equal and opposite directions with equal and opposite momentum
*bullet moves off with equal and opposite momentum as gun recoils |
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Term
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Definition
force = change in momentum/time taken
*the more time an impact takes the less force |
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Term
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Definition
like charges repell.
Unlike charges attract
*When 2 electrically insulating materials are rubbed together electrons are rubbed off 1 onto the other.
which way they go depends on the material
*the material that gains electrons becomes negatively charged |
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Term
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Definition
*rate of flow of charge
*a metal can only hold charge if it is off the ground.
*it is earthed if connected to ground
* the bigger the charge the higher the potential difference between object and earth.
*If high enough then a spark may jump across gap. |
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Term
| uses and dangers of staic electricity |
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Definition
uses eg electrostatic paint sprayer positively charged and item being painted negatively charged then paint spreads out when hits object.
eg photocopiers -copying plate charged so when light hits it black ink powder ia attracted and leaves image.
dangers eg filler pipe on road tanker are earthed so no sparks which would cause explosion |
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Term
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Definition
*a spark can make powder grains expode
*to eliminate static use antistatic materials and earth metal objects |
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Term
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Definition
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Term
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Definition
Resistance is the opposition to charge flowing
resistance= potential difference/current
measures in ohms
*current is measured by an ammeter |
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Term
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Definition
in a filament lamp resistance increases with higher temp of filament
in a diode forward resistance is low, backward resistance is high
in a thermistor resistance decreases if temp increases
in light dependent resistor(LDR) reistance decreases if light increases |
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Term
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Definition
repeatedly reverses direction
*mains electricity is alternating
A mains circuit has a live wire which is alternately positive (+325)then negative (-325)every cycle.
*It also has a neutral wire which is zero volts |
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Term
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Definition
| mains supply has frequency of 50 Hertz which means it alternates 50 times each second |
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Term
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Definition
| current travels in 1 direction only |
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Term
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Definition
cables have 2 or 3 insulated copper wires surrounded by plastic flexible case.
Sockets and plugs made from stiff plastic which enclose electrical connection
*Live wire -BROWN
*Neutral wire -BLUE
*Earth wirw -YELLOW AND GREEN
Pins made of brass as good conductor |
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Term
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Definition
contains a thin wire that melts and cuts off current if too much current flowing through
fuse rating should be slightly higher than the normal working current of appliance |
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Term
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Definition
| electromagnetic switch that opens (trips) and cuts off current if too much passes through |
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Term
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Definition
power = energy transformed/time
measured in watts
Electrical power= current x potential difference |
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Term
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Definition
when electric current flows through an appliance electrical energy is transformed to other forms
energy transformed = potential difference x charge
charge = current x time |
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Term
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Definition
alpha decay nucleus loses 2 protons and 2 neutrons which are emitted as an alpha particle
beta decay neutron changes to proton and an electron is created and emitted as a beta particle |
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Term
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Definition
| rutherford used measurements from alpha scattering experiment to prove that an atom has a small positively charged nucleus which contains most of the mass |
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Term
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Definition
occurs when a neutron collides and splits a uranium -235 nucleus or a plutonium 239 nucleus
chain reaction occurs when neutrons from fission go on to cause further reactions.
In a nuclear reactor every fission causes 1 other fission. |
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Term
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Definition
joining of 2 atomic nuclei to form a single larger nucleus.
During this process energy is released.
This is the process which happens in stars
Nuclei approaching one another repel as they are poitively charged this is overcome by heat and contained by a magnetic field. |
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