PAPER 2 GCSE Flashcards
effects of forces between bodies
Forces can act on a body to change the velocity, so the speed, direction or both.
Or forces can change the shape of a body, stretching it squishing it or twisting it.
Is force a vector or a scalar quantity
Vector
Friction is
A force that opposes motion
Friction is caused by surfaces rubbing. The force always acts in the opposite direction to motion
the stopping distance of a vehicle is made up of
the sum of the thinking distance and the breaking distance
Thinking distance is affected by
Tiredness
Alcohol
speed of the car
Drugs (avoid as drugs can increase or decrease thinking distance)
Braking distance is affected by
Road conditions
Tyre conditions
Brake conditions
speed of the car
mass of the car
Terminal velocity
Initially the only force is weight as drag is proportional to velocity
So the object accelerates downwards
As it accelerates the drag increases as well
So there is a smaller resultant force downwards so a smaller acceleration
Until the object reaches a speed where the drag is equal to the weight meaning there is no acceleration
This velocity is know as terminal velocity.
practical investigate how extension varies with applied force for helical springs, metal wires and rubber bands
Measure the length of your spring without
any hanging masses.
Hang a mass of 100g on the spring
Measure the new length of the spring
Calculate the extension of the spring
Repeat increasing the mass in increments of 100g
Hooke’s law is that
extension is directly proportional to force applied. This is shown by the straight line on the force-extension graph
What is elastic behaviour
the ability of a material to recover its original shape after the forces causing the deformation have been removed
How to use momentum as a safety feature
1) f = change in p / t
2) change in momentum for any surfaces
3) time is increased for (change in momentum)
4) so force is decreased
5) force is what causes injury
Momentum before collision =
Momentum after collision
Newton’s third law
Every action has an equal and opposite reaction.
Eg. Book pushes down on table, table pushes up on book. So book doesn’t accelerate
Weight of a body act through
Its centre of gravity
The principle of moments state that
when the clockwise moments are equal to the anticlockwise moments a body will be in equilibrium.
The upward forces on a light beam supported at its ends vary with
The position of a heavy object placed on the beam
Light waves are
transverse waves and that they can be reflected and refracted
Law of reflection
the angle of incidence equals the angle of reflection
Total internal reflection is used for
transmitting information along optical fibres and in prisms
Meaning of the critical angle
The angle of incidence which produces an angle of refraction of 90 (refracted ray is along the boundary of the surface).
When the angle of incidence is greater than the critical angle, total internal reflection occurs (all light is reflected at the boundary).
This effect only occurs at a boundary from a high refractive index material to a low refractive index material.
Sound waves are
longitudinal waves which can be reflected and refracted
the frequency range for human hearing
20–20 000 Hz
Investigate the speed of sound in air with a oscilloscope
Connect two microphones to an oscilloscope
Place them about 2 m apart using a tape measure to measure the distance between them
Set up the oscilloscope so that it triggers when the first microphone detects a sound, and adjust the time base so that the sound arriving at both microphones can be seen on the screen
Make a large clap using the two wooden blocks next to the first microphone
Use the oscilloscope to determine the time at which the clap reaches each microphone and the time difference between them
Repeat this experiment for several distances
Investigate the speed of sound in air using wooden blocks
Use the trundle wheel to measure a distance of 100 m between two people
One of the people should have two wooden blocks, which they will bang together above their head to generate sound waves
The second person should have a stopwatch which they start when they see the first person banging the blocks together and stop when they hear the sound
This should be repeated several times and an average taken for the time travelled by the sound waves
Repeat this experiment for various distances
how an oscilloscope and microphone can be used to display a sound wave
With the microphone plugged into the oscilloscope, the microphone will transfer the sound into an electrical signal which the oscilloscope can display .The x axis show the time base which can be adjusted, along the y axis voltage is displayed as the wave is converted into an electrical signal this means amplitudes can be compared.
High frequency means
High pitch
The greater the amplitude
The louder the sound
Heating a system will change the energy stored within the system and raise its temperature or produce changes of state
substance must absorb heat energy so that it can boil or melt
high temperatures, particles have more energy
energy can be transferred to particles at a lower temperature
Solids are
Tightly packed
Held in fixed pattern
Vibrate about fixed positions
Liquids are
Tightly packed
Can slide over each other
Gases are
Very spread out
Move with rapid, random motion
obtain a temperature–time graph to show the constant temperature during a change of state
Remove the boiling tube of stearic acid from
the water bath
Place the tube into a beaker of room
temperature water
Add a thermometer to the water
Take readings from the thermometer in the
stearic acid and the water every minute
Note readings in the table
Note on the table when you observe the stearic
acid change from a liquid to a solid.
Plot your results in a graph
Specific heat capacity is
the energy required to change the temperature of an object by one degree Celsius per kilogram of mass (J/kg °C)
Voltage is induced in a conductor or a coil when
it moves through a magnetic field or when a magnetic field changes through it
What affects the size of the induced voltage in a conductor / coil
the strength of the magnetic field, how fast the coil is spinning, how many turns in the coil.
How does a generator (rotating coil) work
· Coil is rotated within a magnetic field
· As it turns the coil cuts the magnetic field lines.
· This induces a voltage (or current) in the coil.
· This can then be connected to an existing circuit.
· In a generator, energy is being converted from kinetic (mechanical) energy into electrical energy.
The size of the induced voltage (or current) in a generator can be increased by
· Using a stronger magnet
· Having more turns in the coil
· Spinning/moving the coil faster.
How does a generator work (rotating magnet)
· Magnet is rotated within a coil
· As it turns the coil cuts the constantly changing magnetic field lines from the magnet.
· This induces a voltage (or current) in the coil.
· This can then be connected to an existing circuit.
· In a generator, energy is being converted from kinetic (mechanical) energy into electrical energy.
Structure of a transformer
AC current in the primary coil produces a changing magnetic field around the primary coil.
The iron core channels the changing field through the secondary coil.
The changing magnetic field induces a voltage in the secondary coil.
How does a transformer change the size of an alternating voltage by having
different numbers of turns on the input and output sides
Step up transformers
increase the voltage – more secondary turns than primary
Step down transformers
decrease the voltage – more primary turns than secondary
Where are step up and step down transformer used
in the large-scale generation and transmission of electrical energy
Nuclear fission
The process where heavy atoms are split into smaller, lighter atoms. This releases energy
Nuclear fusion
The process where lighter atoms are forced to join together to make heavier atoms. This releases energy.
Radioactive decay provides energy
Within the core of the Earth, radioactive isotopes of elements provide a large proportion of the heat within the Earth through radioactive decay.
What does the fission of U-235 producen
two radioactive daughter nuclei and a small number of neutrons
How does fission of uranium 235 occur
A slow moving neutron is absorbed by a uranium 235 nucleus (collision of a neutron)
The resulting uranium 236 nucleus is unstable.
How does fission release energy
As kinetic energy of the fission products
describe how a chain reaction can be set up if the neutrons produced by one fission strike other U-235 nuclei
The three neutrons produced by the fission may hit other nuclei of uranium 235, causing the process to repeat.
For a chain reaction to occur, there is a minimum mass of uranium 235 required. This is known as the critical mass.
Control rods
The purpose of the control rods is to absorb neutrons and completely remove them from the fission process.
Helps adjust the rate of nuclear fission in the reactor (stops the reaction)
Moderator
The purpose of the moderator is to absorb some of the kinetic energy of the neutrons to slow them down.
This makes the reaction faster because slow neutrons are more easily absorbed by uranium 235 nuclei.
the role of shielding around a nuclear reactor
Reactor vessel is made of steel and surrounded by a concrete layer about 5 meters thick.
This prevents any radiation escaping, even neutrons.
the difference between nuclear fusion and nuclear fission
Fission – Larger nuclei are split into smaller nuclei
Fusion – Two smaller nuclei collide and combine to form a larger nucleus
Fusion is the energy source for
for our sun and all stars.
In the case of the sun, it is typically hydrogen undergoing fusion to create helium.
why nuclear fusion does not happen at low temperatures and pressures
very high temperatures are required to overcome the repulsive force between the positively charged nuclei of each isotope.
High pressures are also needed to increase the chance of fusion between the nuclei.
describe the past evolution of the universe and the
Scientists believe that about 14 billion years ago all matter in the Universe was in one extremely tiny and dense place. It then suddenly exploded, and has been expanding ever since
CMBR evidence
Microwave radiation can be detected EVERYWHERE in the Universe. These are the stretched remains of high energy gamma radiation that would have been produced in the explosion that created the Universe. They have stretched because the Universe is expanding.
Red shift evidence
If we examine the light for distant galaxies we can see that the wavelengths of the light have become longer. We call this stretching of the waves ‘red-shift’. It tells us that the galaxies producing the light are moving away from us .The further away a galaxy is, the greater its red-shift, so it is moving even faster. This is evidence that the space between all the galaxies is stretching and the Universe is expanding and so it supports the Big Bang Theory.
if a wave source is moving relative to an observer there will be a change in
the observed frequency and wavelength
