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Q: What is the relationship between speed, distance and time?
Distance = speed x time
Q: What is velocity?
A: Speed in a given direction.
Q: What is acceleration?
A: The rate that an object's speed is increasing.
Q: What is the relationship between acceleration, velocity change, and time?
A: Velocity change = acceleration x time
Q: How can distance travelled be calculated from a velocity-time graph?
A: It is the area under a graph.
Q: What is total stopping distance?
A: The distance between a driver seeing a stimulus and the car coming to a stop. (Braking distance + thinking distance)
Q: What is thinking distance?
A: The time between when a driver sees something and when the driver presses the brake.
Q: What is Braking distance?
A: The time a car takes to stop once the brake has been pressed.
Q: What factors affect thinking distance?
A: Velocity of car, reaction time(tiredness/alcohol/drugs/old age), if driver is distracted.
Q: What factors affect Braking distance?
A: Velocity of car, mass of car, brake condition, tyre condition, road condition, weather.
Q: What are the two ways of reducing force on occupants during collision?
A: Reducing the speed of the collision, increasing the time for a collision.
Q: Give examples of safety features in modern cars.
A: Seat belts, air bags, crumple zones.
Q:How do seat belts, air bags and crumple zones reduce the force on occupants during a collision.
A: They increase the time of a collision by allowing themselves to be (slowly) deformed during a collision.
Q: What are the ways that car speed is restricted?
A: Speed limit, Speed bumps.
Q: What is inertia?
A: The opposition of an object to a change in its motion (or rest).
Q: What dictates how easy it is to change an object's motion, and what is this property called?
A: Mass, inertia.
Q: What is Newton's first law?
A: 'An object at rest stays at rest or an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force' (an object maintains its velocity unless acted upon by an unbalanced force).
Q: If forces acting on it are balanced, what will an object do?
A: Continue moving (or not) at the same velocity.
Q: If forces acting on it are unbalanced what will an object do?
A: Accelerate in the direction the strongest force is acting.
Q: What equation is Newton's second law summarised as?
A: Acceleration = resultant force/mass.
Q: If a car has its engine on, why will it not accelerate forever?
A: The car will accelerate until the increasing air resistance acting on it will make the forces balanced. Then it will move at a constant speed.
Q: What is the difference between weight and mass?
A: Mass is a measure of the matter in an object, while weight is how much force it exerts on whatever is under it, it is dependent on gravitational field strength.
Q: What is the relationship between weight, mass and gravitational field strength?
A: Weight = mass x gravitational field strength.
Q: What is the gravitational field strength of earth?
A: 10 N/Kg
Q: What is Newton's third law?
A: 'For every action force, there is an equal and opposite reaction force'.
Q: If rugby players push on a scrum machine with a force of 5N, what is the reaction force of that?
A: The machine pushes on them with a force of 5N.
Q: What are three things that must be considered when using Newton's third law?
A: Forces act on a different object, forces are equal in size and opposite in direction, forces are the same type(e.g.- gravitational/contact/electrical/magnetic).
Q: What is work?
A: A measure of the energy transferred from one object to another.
Q: What is the relationship been force, distance moved in the direction of the force, and work done?
A: Work done = force x distance moved in the direction of force.
Q: Why may work done not equal the total energy transferred?
A: Energy is often lost as heat to surroundings (e.g.- as air resistance or friction).
Q: What is gravitational potential energy dependent on?
A: Mass, gravitational field strength, height?
Q: How can gravitational potential energy be calculated?
A: Gravitational potential energy) = mass x gravitational field strength x change in height.
Q: What is kinetic energy?
A: A form of energy represented by an object moving.
Q: How can the kinetic energy of a moving object be calculated?
A: Kinetic energy = 1/2 x mass x velocity x velocity.
Q: Describe the gravitational potential energy and kinetic energy in a ball which has been thrown upwards.
A: The ball begins with lots of kinetic energy and loses this (the ball gets slower) as the gravitational potential energy increases. Then the ball begins to lose gravitational potential energy (the ball descends) and kinetic energy increases. When the ball lands energy is converted to heat, sound, or elastic potential if the bowl is bouncy.
Q: What is the spring constant?
A: A measure of the stiffness of a spring, smaller is more stretchy.
Q: What is the relationship between force, spring constant, and extension.
A: Force = Spring constant x extension.
Q: Why is more work needed to stretch a spring than the (force = Spring constant x extension) equation indicates?
A: The force equation means that if that force was continually applied to the spring would only ever stretch that far. In work done, energy is needed to stretch the spring to every amount of extension before.
Q: What is a force-extension graph?
A: A graph with force as a y axis and extension as an x axis, the line's gradient is dependent on the spring constant.
Q: In a spring that doesn't obey F = kx (e.g.- one that you're beginning to deform), how would you calculate work needed to stretch or compress a spring to an amount?
A: Area under a force-extension graph.
Q: Where a spring obeys F = kx, what equation can be used to calculate work done on a spring?
A: Work = 1/2 x Force x Spring extension
Q: What are the five ways vehicles can be made more efficient?
A: Improving aerodynamics, Lowering bottom of vehicle, Better tyres, reducing energy lost when vehicle is stopped, using lighter materials?
Q: How can improving aerodynamics increase efficiency of a vehicle?
A: It allows the air to move more smoothly past them so less work is done forcing air away. It increase the fuel economy and range of a vehicle.
Q: How can lowering a vehicle's bottom improve its efficiency?
A: It means the wheels are more enclosed within wheel arches which increases aerodynamics and improves fuel economy.
Q: How can better tyres improve the efficiency of a vehicle?
A: Tyres should be designed so they have enough grip to ensure passenger safety, and as little rolling resistance between the tyre and road surface. Once this balance is found, fuel economy can be improved without sacrificing passenger safety.
Q: How can reducing energy loss when vehicle is idle improve that vehicle's efficiency?
A: Computers operate now to shut down a cars engine if it is not being used which increases fuel economy. Alternatively, some engines charge their electric batteries when the car is idle.
Q: How can making a vehicle with lighter materials increase that vehicle's efficiency?
A: If the car has less mass it reduces its inertia so less energy is required to move it in the first place.
Q: What is momentum?
A: The product of mass and velocity for an object: how much force is required to stop an object.
Q: How can the force required to change an object's momentum be calculated?
A: Resultant force = Change in momentum / Time for change.
Q: What is the law of conservation of momentum?
A: Total momentum before collision/interaction = Total momentum after collision/interaction.
Q: What is an elastic collision?
A: A collision where total kinetic energy before the collision is equal to the total kinetic energy after the collision.
Q: Why are very few (if any) collisions truly elastic?
A: Because most collisions involve energy loss such as heat or sound.
Q: What does x stand for in the equations of motion?
A: Distance travelled in metres.
Q: What does u stand for in the equations of motion?
A: The initial velocity of an object.
Q: What does v stand for in the equations of motion?
A: The final velocity of an object.
Q: What does a stand for in the equations of motion?
A: Acceleration of an object.
Q: What does t stand for in the equations of motion?
A: Time of an object's motion.
Q: In the equations of motion, where an object is falling what is often used instead of a?
A: g, the gravitational constant, 10 on earth.
Q: What is a moment?
A: The turning force that acts on a pivot, measured in Newton metres.
Q: How can moments be calculated?
A: Moment = Force x distance from pivot.
Q: What is the principle of moments?
A: Where the sum of anticlockwise moments equals the sum of clockwise moments, an object is in balance.
Q: What is in the solar system?
A: 1 star(the sun), 8 planets, 5 dwarf planets, 146 moons, an asteroid belt between Mars and jupiter, and many rocks.
Q: List all eight planets in order from the sun.
A: Mercury, Venus, Earth, Mars, (asteroid belt) Jupiter, Saturn, Uranus, Neptune (Mary's 'virgin' explanation makes Joseph suspect upstairs neighbour).
Q: What is the relationship between orbital radius and orbital period of a planet?
A: As orbital radius increases, orbital period increases erratically.
Q: What does R⨁ mean?
A: It is a unit that measures the radius of planets proportional to earth. 1 R⨁ is Earth's radius and 11R⨁ is Jupiter's radius.
Q: What is an AU?
A: An astronomical unit. It is a unit of distance which is equal to the average distance between the earth and the sun. Neptune is 30 AU from the sun, and the solar system's farthest stretches are 100,000 AU from the sun.
Q: What is a light year?
A: The distance light travels in one year. Our solar system is around 4 ly away.
Q: Describe our position in the universe.
Our solar system is in the milky-way galaxy, which is part of a 'local group' of galaxies. That 'local group' is part of the Virgo supercluster around 110 million ly across. The Virgo supercluster is one of the largest observed structures in the universe.
Q: What is a nebula?
A: A gas and dust cloud that results from the supernova death of a huge star.
Q: What is a protostar?
A: A part of a nebula which has been formed because the nebula is collapsing due to gravity. The nebula is also collapsing due to gravity. A protostar is the stage in a star's formation before nuclear fusion starts.
Q: What happens to a protostar?
A: It collapses further due to gravity and gas and dust from the surrounding nebula are drawn into it. The temperature inside the core increases and when this temperature exceeds 15 million °c, nuclear fusion reactions of hydrogen gas begin and a main-sequence star is born.
Q: What is a main-sequence star?
A: A star that releases energy by fusing hydrogen into helium.
Q: What is the Hertzsprung - Russell diagram?
A: A means of displaying the properties of stars and depicting their evolutionary paths. It is a scatter graph with heat against light.
Q: What stars are found in the top -right of most Hertzsprung - Russell diagrams (Cool and bright)
A: Red super-giants.
Q: What stars are found in the top -left of most Hertzsprung - Russell diagrams (Hot and bright)
A: The largest main sequence stars.
Q: What stars are found in the Bottom-right of most Hertzsprung - Russell diagrams (Cool and dim)
A: The smallest main-sequence stars.
Q: What stars are found in the bottom-left of most Hertzsprung - Russell diagrams (hot and dim)
A: White dwarf stars.
Q: What is a red giant star?
A: The phase after main-sequence stars, the star has run out of hydrogen fuel so begins to fuse helium into heavier elements.
Q: In What stellar phase do most stars spend most of their lifetime.
A: As main-sequence stars.
Q: Why may main-sequence stars explode or implode?
A: They may implode because of their strong gravitational force, they may explode because of the gas pushing out or the radiation pressure (electromagnetic radiation moving out from the star's core).
Q: Why is a red giant bigger and cooler than a main - sequence star?
A: The star increasingly relies on nuclear fusion so the electromagnetic radiation is stronger and the star is pushed outwards by its electro-magnetic radiation, it still has the same energy so the heat is spread over a much larger space. The star is thus cooler.
Q: What is a white dwarf?
A: A star where fusion no longer occurs. It is cooling.
Q: What happens to a white dwarf star?
A: It becomes a red dwarf star then finally a black dwarf star.
Q: Why do red giants become white dwarfs?
A: As the red giant progresses it relies on fusing helium into heavier and heavier elements. After iron, the star can no longer gain energy from this and fusion stops. The star collapses and its outer atmosphere is puffed outward and becomes a planetary nebula. The rest is termed a white dwarf.
Q: List the components in the life cycle of the sun.
A: Protostar, main sequence, red giant, planetary nebula, white dwarf, red dwarf, black dwarf.
Q: What happens to massive main-sequence stars?
A: They swell up to form red super-giants and when nucleo-synthesis stops in this, the supergiant undergoes rapid collapse and the resulting explosion is called a supernova.
Q: What is nucleo-synthesis?
A: Where red giants and supergiants produce heavier and heavier elements.
Q: When is the only time that elements heavier than iron are formed?
A: During a supernova collapse.
Q: What is left after a supernova explosion in 'low' mass supergiants?
A: Huge nebulae, with enough gas and dust to start stellar formation again.
Q: What is left after a supernova explosion in 'high' mass supergiants?
A: A neutron star, an enormous amount of matter compressed into a radius of about 12 km. Many neutron stars rotate at high speeds and emit huge beams of electromagnetic radiation as they do so. A neutron star is pure neutrons.
Q: What is left after a supernova explosion in 'superhigh' mass supergiants?
A: Black holes, the most concentrated form of matter compressed into a space of about 30km. Not even light can escape from its pull. (which is why it's black).
Q: What is stellar spectroscopy?
A: A way of determining the composition of stars. The spectra of a star is found and this spectra will have black lines where wavelengths have been removed because they were absorbed by elements in the star. Therefore, the particular elements can be discovered.
Q: What is a spectrum?
A: All the colours from purple to red. All stars emit a spectrum although sometimes this does not show on earth because it has been absorbed by particular elements.
Q: What is cosmological redshift?
A: Because the universe is expanding, light slowly gets more red. (Space increases so the wavelength of light also does).
Q: What is hubble's law?
A: The increase in redshift is proportional to the distance away from earth.
Q: How can we measure the distance of things from earth?
A: It is proportional to redshift. If light is travelling for longer, the wavelength is increasing for longer.
Q: What is the big bang theory?
A: The idea that the universe began with an explosion and is still expanding today. It also predicts that enormous amounts of energy in the form of gamma rays was produced.
Q: What is CMBR?
A: Cosmic microwave background radiation, discovered in 1946.
Q: What two facts provided evidence for the big bang theory?
A: Cosmic microwave background radiation and cosmological redshift.
Q: How does Cosmic microwave background radiation provide evidence for the big bang theory?
A: Assuming the big bang emitted gamma rays. These would now be redshifted enough that they would be microwaves by now. These waves are now the background microwave radiation.
