Physics - Revision
Criteria D: Reflections on impact of science writing format
(Always include paragraphs) (no personal pronouns) 1) Physics behind the concept 2) factors 3) factors 4) 2 advantages 5) 2 disadvantages 6) conclusion Factors: social (how it impacts humans), Moral (is it right or wrong? religion), Ethical (is it right or wrong? human), Environmental, Political, Economical HAVE TO INCLUDE THE ACTUAL NAME OF OF THE FACTOR!!
Centre of gravity
Centre of gravity, of an object, is the point at which weight is evenly dispersed and all sides are in balance. A good rule of thumb is that masses with a wider base have lower center of gravities while objects with narrower bases have higher centers of gravity. The image to the left illustrates the earlier statement. The wider cars have a lower center of gravity making it harder for them to topple over as compared to the narrower bus. As the center of gravity of the mass shifts past the edge of the object, the object will become unstable and topple over.
Law of Conservation of Momentum
For a collision occurring between object 1 and object 2 in an isolated system, the total momentum of the two objects before the collision is equal to the total momentum of the two objects after the collision. That is, the momentum lost by object 1 is equal to the momentum gained by object 2. The above statement tells us that the total momentum of a collection of objects (a system) is conserved - that is, the total amount of momentum is a constant or unchanging value.
Forces, strength and distance of action
Force Strong nuclear Relative strength (compared to strong nuclear = 1) 1 Distance of action (m) <10^-15 Force Electromagnetic Relative strength (compared to strong nuclear = 1) 1/137 = 7.2x10^-3 Distance of action (m) infinite Force Electroweak Relative strength (compared to strong nuclear = 1) Approx. 10^-6 Distance of action (m) 10^-18 Force Gravity Relative strength (compared to strong nuclear = 1) 6x10^-39 Distance of action (m) infinite
Action-reaction pairs
Forces always come in pairs - known as "action-reaction force pairs." The baseball forces the bat to the left; the bat forces the ball to the right. Together, these two forces exerted upon two different objects form the action-reaction force pair. Note that in the description of the two forces, the nouns in the sentence describing the forces simply switch places.
Vectors
Forces are vectors, which means they have both direction and magnitude. Force arrows can be used to show the direction of the force and the size of the force. An example of this can be the force of thrust and air resistance acting on an aeroplane as it flies through the air.
What can forces cause?
Forces can cause a change in shape, motion, direction or speed.
Distance, Speed and Time
Formulas: Speed = Distance / Time, Distance= Speed x Time, Time= Distance / Speed Speed is measured in m/s or ms^-1 Example: If Ben traveled 50 mph for 3 hours, 60 mph for 2 hours, and 70 mph for 1 hour, what was his average speed for the entire trip? First, the distance and time values need to be identified. 50 kmph x 2 hours = 100 km 60 kmph x 1 hour = 60 km 70 kmph x 1/2 hour = 35 km Total distance= 100+60+35= 195 km Total elapsed time= 2+1+½= 3½ hours 195 km/3½ hours= 55.71 kmph Converting from km/h to m/s 55.71 x 1000= 55710 m/hr 55710 m/hr/3600= 15.475 m/s
Momentum
Momentum refers to the quantity of motion that an object has. Momentum can be defined as "mass in motion." All objects have mass; so if an object is moving, then it has momentum - it has its mass in motion. Momentum = mass • velocity p = m • v where m is the mass and v is the velocity. The equation illustrates that momentum is directly proportional to an object's mass and directly proportional to the object's velocity. The units for momentum would be mass units times velocity units. The standard metric unit of momentum is the kg•m/s.
Trignometery
SOHCAHTOA sin= opp/hyp cos= adj/hyp tan= opp/adj for missing side lengths ex: the hypotenuse is 13cm and an angle is 70 degrees x is opp and needs to be found you need to do opp/hyp as those are the two values you have and need sin 70= x/13 x= 13 sin 70 x= 10.06 Eric leaves base camp and hikes 11km north and then hikes 11km east. What is his resultant force? You have a and b, and you are looking for c the hypotenuse 11^2+11^2=242 c^2=242 c= root 242 c= 15.6 Now you are trying to find angle opp a. sin= opp/hyp sin teta = 11 km /15.6 km = 0.7051 teta= sin^-1(0.7051)= 45 degrees
Newton's second law of motion
Second Law: Acceleration is produced when a force acts on a mass. The greater the mass (of the object being accelerated) the greater the amount of force needed (to accelerate the object). Exact relationship between force and mass F=MA.
Show the uncertainty of measurements
Show the uncertainty of measurements Addition and Subtraction Add the values Ex: 1.2 ± 0.1, 12.01 ± 0.01, 7.21 ± 0.01 1.2 + 12.01 + 7.21 = 20.42 0.1 + 0.01 + 0.01 = 0.12 20.42 ± 0.12 b. Multiplication and Division Multiply the values Ex: 1.2 ± 0.1, 12.01 ± 0.01 1.2 x 12.01 = 14 0.1 / 1.2 x 100 = 8.33 % 0.01 / 12.01 X 100 = 0.083% 8.33 + 0.083 = 8.413 % 14 ± 8.413 %
Unbalanced forces
When two forces acting on an object are not equal in size, we say that they are unbalanced forces. The overall force acting on the object is called the resultant force.
Outline the variables that affect the choice of design in a structure, particularly in terms of physical properties of materials
When you draw a diagram, you must consider, other than the force directions and force magnitudes, the physical properties of the materials the forces are acting on, including: ● Size: A bigger or heavier (or both) object creates more require bigger forces to move or balance than a smaller or lighter (or both) object. (an armchair and a cm3 of cheese) ● Length: an object much longer than wide would experience a different tension depending on the strength of the force applied on it (eg a rope in Tug of War) ● Shape: an object with a smoother and regular shape would create less resistance to some kinds of forces (pull/push, air resistance, friction) than a shape with angles and irregularities. Also, the less surface touches a surface in proportion, the more effect will have some kinds of forces on the object (eg. a sphere and a cube) ● Animated/inanimate object: An animated object would probably exercise by itself a force (push or pull, friction), which might be irregular in terms of direction and constant strength, while an inanimate object would only experience the forces (a dog and a pen)
Pythagoras Theorem
a^2+b^2=c^2 Eric leaves base camp and hikes 11km north and then hikes 11km east. What is his resultant force? You have a and b, and you are looking for c the hypotenuse 11^2+11^2=242 c^2=242 c= root 242 c= 15.6
Forces on a incline plane
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Powers, units and names
10^-15 femto fm 10^-12 pico pm 10^-9 nano nm 10^-6 micro mu 10^-3 milli mm 10^-2 centi cm 10^3 kilo km 10^6 mega Mm 10^9 giga Gm 10^12 tera Tm
Effect of air resistance and gravity on a falling object
A falling object will continue to accelerate to higher speeds until they encounter an amount of air resistance that is equal to their weight. Massive objects fall faster than less massive objects because they are acted upon by a larger force of gravity; for this reason, they accelerate to higher speeds until the air resistance force equals the gravity force.
Light year
A light year is the distance covered by light in one year (9.461 x10^12)
Mass spectometer
A mass spectrometer measures the mass of a single atom or molecule, basically the smallest objects... in other words. First the atoms must be heated to a gas state. Then they are bombarded with high speed electrons to knock electrons free from the sample gas.
Singularity
A singularity is when an infinite amount of gravitational density is focused on one point.
Big Bang Theory
According to the Big Bang Theory, all the matter and energy in the Universe compressed into a very small space. Then it exploded, and started expanding, and the expansion is still going on now. The age of the Universe can be estimated from the current rate of expansion, where the estimate age of the Universe is 13.7 billion years.
Kepler's first law
All planets move around the Sun in elliptical orbits, with the sun at one focus. (Law of Orbits)
Bar magnets
Bar magnets and all magnetic fields have south poles and north poles where the same poles repel while opposite poles attract There is a flow from north to south as shown in the image above where all magnetic force that flows out of the north side flows back into the southside
What is the universe made of?
Dark matter, normal matter, and dark energy 26% of the universe is observable 74% of the universe is invisible dark matter does not emit light, energy or take up space dark energy is mostly unknown but it affects the universe's expansion and takes up most of the energy in the universe.
Problems created by an invariant speed of light
Having an invariant speed of light prohibits travel faster than the speed of light. This comes from the theory of relativity. As an object increases in speed, its mass also increases. For small speeds this effect is negligible. But at the speed of light, this causes any energy applied to the object to be converted into mass, and not actually increase the speed at all.
Theory of relativity
Massive objects cause a distortion in space-time, which is felt as gravity.
Olber's paradox
Olber's paradox is the argument that the darkness of the night sky conflicts with the assumption of an infinite and eternal universe. The darkness of the sky proves that the universe is expanding as we do not see billions and billions of stars around us as they are moving further away.
Experimental inquiry (Rationalism, Variable, Empiricism, Experiment)
Rationalism - the practice or principle of basing opinions and actions on reason and knowledge rather than on religious belief or emotional response. Ex: people believing that the earth is round, big bang theory. Variable - an element, feature, or factor that can vary or change. Ex: control (kept the same), independent (changed) and dependent (measured) variables Empiricism - the theory that all knowledge is based on experience derived from the senses. Ex: knowing that a tree is brown and green by looking at it Experiment - a scientific procedure undertaken to make a discovery, test a hypothesis, or demonstrate a known fact.
Reflecting telescope
Reflecting telescope (Reflector) - This uses curved mirrors to reflect and focus the light.
Refracting telescope
Refracting telescope (Refractor) - This uses lenses to refract and focus the light.
Ray Diagrams
Rules for ray diagram construction: Parallel Ray: A ray parallel to the optical axis passes through the focal point on the other side of the lens. Focal Ray: A ray that passes through the focal point emerges parallel to the optical axis on the other side of the lens. Centre Ray: A ray that passes through the center of the lens continues with no change in direction.
SI Units
SI Units - A set prefix to indicate the multiplication or division by a power of 10. Mass Kilogram (kg) Time Seconds (s) Length Meter (m) Temperature Kelvin (K) Force Newtons (N) Pressure Pascal (Pa) Energy Joule (J)
Scalar and vector quantities
Scalar quantity: is described by magnitude only ex: 20kg weight and friction Vector quantity: is described by magnitude and direction. (ex: 20n right thrust) speed, temperature
Special theory of relativity and its posulates
Special relativity only applies to specific situations where the different frames of reference are not accelerating. 1. The Principle of Relativity The laws of physics are the same in all inertial frames of reference. 2. The Constancy of Speed of Light in Vacuum The speed of light in vacuum has the same value c in all inertial frames of reference. The speed of light in vacuum c (299792458 m/s) is so enormous that we do not notice a delay between the transmission and reception of electromagnetic waves under normal circumstances. The speed of light in vacuum is actually the only speed that is absolute and the same for all observers as was stated in the second postulate.
Speed of light
The speed of light is 299 792 458 m / s To calculate time in seconds take to cover distance in m, divide distance by speed. E.g. to calculate how long it will take to cover 10,000,000 Km: Convert km to m : 10,000,000,000 m Divide distance by speed: 10,000,000,000 / 299 792 458 Answer: 33.3564095198 seconds
Steady state and expansion model
The steady state theory is a view that the Universe is constantly expanding, but maintains a constant average density. This happens with matter constantly being created to form new stars and galaxies at the same rate as old ones become unobservable due to increasing distance . A steady state Universe has no beginning or end in time. Edwin hubble discovered the red shifting of light from galaxies across the universe. This led him to discover that galaxies were moving apart from each other at great speed, and that the universe was therefore definitively growing in size. In effect, all the galaxies we see are slightly red in colour due to redshift. This is the expanding model of the universe, where the universe is continually expanding.
Explain how sufficient, relevant data can be collected
Using appropriate apparatus to measure results Testing results relevant to the experiment Repeating the procedure multiple times to achieve more accurate results
Balanced forces
When two forces acting on an object are equal, we say they are balanced forces.
Astronomical Unit, Size of Solar System, Milky way galaxy and known Universe. Diameter of earth, sun, earths orbit, solar system, distance from sun to nearest star and distance from milky way to nearest galaxy
1 AU - Astronomical Unit = 149,597,871 km = mean distance from the centre of the Earth to the centre of the Sun - 1.5x10^9 m Size of Solar System= 100,000 AU or 1.87 light years or 8.03 x 10^13 m Size of the Milky way galaxy= 100,000 light years (diameter) - 8.02x10^17 m or 10^21m Size of the known Universe= The observable universe is a sphere with a diameter of about 28.5 gigaparsecs (93 Gly or 8.8×10^26 m). Diameter of the Earth= 13,000 km Diameter of Sun= 1.3914 million km From milky way galaxy to nearest galaxy - 2.5 million light years Diameter of the Solar System - 287.46 billion km Diameter of the Earth's orbit - 144 million km Distance from the sun to nearest star - 4.24 light years
Conversion factors
454g = 1 pound 750g = ? 1/454 x 750/1 = 1.6519lb 750g= 1.6519lb (1)/(2)x(3)/(4) 1: the unit that you are trying to find, but it's single value ex: 1 2: the unit you already know and the amount you already know. Ex: 454g in the example. 3: The unit you know but trying to find its corresponding value in a different conversion. Ex: 750g 4: the unit that you are trying to find, but it's single value ex: 1
The properties of some deep space objects: nebulae (both star-forming and supernova remnant), pulsars, other galaxies
A nebula is an interstellar cloud of gas and dust. Emission nebulae are powered by young, massive stars and emit their own light, reflection nebulae shine by reflecting light from nearby massive stars, and dark nebulae are dark and can only be seen when silhouetted against a bright background. Nebulae can also result from the end stages of stellar evolution. In this case they are present as either a planetary nebula or a supernova remnant depending on the mass of the dying star. A pulsar is a celestial object, thought to be a rapidly rotating neutron star, that emits regular pulses of radio waves and other electromagnetic radiation at rates of up to one thousand pulses per second. A galaxy is a gravitationally bound system of stars, stellar remnants, interstellar gas, dust, and dark matter.
Kepler's second law
A radius vector (a straight line) joining any planet to the Sun sweeps out equal areas in equal lengths of time. (Law of Areas)
Accelerating and Constant Velocity
Accelerating: When an object increases its speed over time. Fp ---->------>--------->--------------> Fg | | | Constant velocity: when an object moves at the same rate of speed constantly Fp ------> Fg | | |
Acceleration
Acceleration, is the rate of change of velocity of an object with respect to time. An object's acceleration is the net result of any and all forces acting on the object, as described by Newton's Second Law Acceleration depends on the force applied to an object and the object's mass.
Distinguish between accuracy and precision
Accuracy Accuracy is defined as how close the measurement is to its true value Precision Precision is defined as the consistency in results when measurements are repeated Ex: 99, 98, 100, 102, 101 (100 is the true value) Ex: 91, 92, 91, 91, 92
Aristotle and Galileo
Aristotle believed that objects of different masses fell at different rates, proportional to the mass of the object. Aristotle distinguished between two types of forces: Natural and unnatural. He believed that natural motion was induced by the need for things made of the same 'element' to be together. He believed that that was the reason that rocks fell towards the earth. He believed that unnatural motion, such as firing a cannonball, required a constant Galileo discovered that all bodies accelerate at the same rate regardless of their size or mass. Galileo developed the concept of motion in terms of velocity, (speed and direction) through the use of incline planes. Galileo discovered that a cause for motion was force Galileo developed the concept of inertia, where objects resist a change in motion. This is implemented in Newton's first law of motion, which states, objects in motion will stay in motion unless acted upon by an unbalanced force. Objects at rest will stay at rest unless acted upon by an unbalanced force. Galileo determined that an object is either in a state of rest or in uniform motion
Life Cycle of a Star
Average Star Sequence Stars are born in a region of high-density Nebula, and condenses into a huge globule of gas and dust and contracts under its own gravity. A region of condensing matter will begin to heat up and start to glow forming Protostars. If a protostar contains enough matter the central temperature reaches 15 million degrees centigrade. At this temperature, nuclear reactions in which hydrogen fuses to form helium can start. The star begins to release energy, stopping it from contracting even more and causes it to shine. It is now a Average Star. A star of one solar mass remains in main sequence for about 10 billion years, until all of the hydrogen has fused to form helium. The helium core now starts to contract further and reactions begin to occur in a shell around the core. The core is hot enough for the helium to fuse to form carbon and will continue to fuse into heavier elements. The outer layers begin to expand, cool and shine less brightly. The expanding star is now called a Red Giant. The helium core runs out, and the outer layers drift of away from the core as a gaseous shell, this gas that surrounds the core is called a Planetary Nebula. The remaining core (80% of the original star) is now in its final stages. The core becomes a White Dwarf the star eventually cools and dims. When it stops shining, the now dead star is called a Black Dwarf. Main sequence star sequence Stars are born in a region of high density Nebula, and condenses into a huge globule of gas and dust and contracts under its own gravity. A region of condensing matter will begin to heat up and start to glow forming Protostars. If a protostar contains enough matter the central temperature reaches 15 million degrees centigrade. At this temperature, nuclear reactions in which hydrogen fuses to form helium can start. The stars shine steadily until the hydrogen has fused to form helium ( millions of years in a massive star). The star begins to release energy, stopping it from contracting even more and causes it to shine. It is now a Main Sequence Star. The massive star then becomes a Red Supergiant and starts of with a helium core surrounded by a shell of cooling, expanding gas. In the next million years a series of nuclear reactions occur forming different heavy elements in shells around the iron core. The core collapses in less than a second, causing an explosion called a Supernova, in which a shock wave blows of the outer layers of the star. (The actual supernova shines brighter than the entire galaxy for a short time). Sometimes the core survives the explosion. If the surviving core is between 1.5 - 3 solar masses it contracts to become a a tiny, very dense Neutron Star. If the core is much greater than 3 solar masses, the core contracts to become a Black Hole.
Newton's first law of motion
First Law: An object at rest will remain at rest unless acted on by an unbalanced force. An object in motion continues in motion with the same speed and in the same direction unless acted upon by an unbalanced force. This law is often called "the law of inertia".
Uses and what are diamonds and graphite?
Diamonds are composed almost entirely of the element carbon, often with some other impurities in them, such as nitrogen. Diamonds are used for grinding, cutting, drilling and polishing because they are durable, resistant to heat, and transparent. Graphite is a mineral compound exclusively of the element carbon. The molecular structure of Graphite and Diamond is entirely different, which causes almost opposite characteristics in their physical properties. Graphite is known as a dry lubricant. It is useful in applications where "wet" lubricants, such as oil, cannot be used. It is a solid material and is a good conductor of electricity. It is used in pencils.
Scales of measurements (magnitudes) length, mass, time
Distance The smallest known length in the universe in some modern theories is the planck length which is 10^-35 m The extent of the observable universe is 10^26 m Distance to Andromeda galaxy is 10^22m Diameter of the Milky way galaxy is 10^21m Distance to nearest star is 10^16m Diameter of the Sun is 10^9m Diameter of the Solar System is 10^13m Radius of the earth is 10^7m Size of a cell is 10^-5m Size of a hydrogen atom is 10^-10m Size of a proton or neutron is 10^-15m Mass The mass of an electron is 10^-30 kg The mass of the Milky way galaxy is 10^41 kg The mass of the Sun is 10^30 kg The mass of the Earth is 10^24 kg The mass of a Boeing 747 is 10^5 kg The mass of the universe is 10^53 kg The mass of an apple is 0.2 kg The mass of a raindrop is 10^-6 kg The mass of a bacterium is 10^-15 kg The mass of the smallest virus is 10^-21 kg The mass of a hydrogen atom is 10^-27 kg Time The planck time is 10^-43s The passage of light across a nucleus is 10^-23 seconds The age of the Earth is 10^17 seconds The age of the universe is 10^17 seconds One year is 10^7s One day is 10^5s
Distance, speed and time, force, acceleration and mass
Distance (d) = Speed (s) x Time (t) Time (t) = Distance (d) / Speed (s) Speed (s) = Distance (d) / Time (t) A dog runs from one end of the park to another. The park is 80 metres across. The dog runs at 5m/s. How long does it take the dog to run from one end of the park to the other? D = 80 m S = 5 m/s T = D/S = 80/5 = 16 seconds Mass is related to force and acceleration. Mass will stay the same, regardless of any changes in gravity or acceleration. Mass should be measured in kg when being calculated with force. Force (f) = Mass (m) x Acceleration (a) (m/s^2) Mass (m) = Force (f) / Acceleration (a) (m/s^2) What is the mass of an object when it is falling down on Earth while exerting 40 N of force? M = F (40 N) / Acceleration (10) = 40 / 10 M = 4 kg
Formulas
Distance (d) = Speed (s) x Time (t) Time (t) = Distance (d) / Speed (s) Speed (s) = Distance (d) / Time (t) Force (f) = Mass (m) x Acceleration (a) Mass (m) = Force (f) / Acceleration (a) W=mg, where W=weight, m=mass and g=gravity. w f ------ or ------ m | g m | g Law of moments: Force 1 (N) x its distance from the fulcrum (m) = Force 2 (N) x distance from the fulcrum (m) Moment (Nm) = force (N) x distance from fulcrum (in m) m ------------ f | d Hooke's Law: f=kx f= force in newtons (n) k= spring constant (n/m) x= distance from equilibrium (m) gravitational field strength: g=f/m f= force m= mass in kg g= gravitational field strength momentum: Mass x velocity p= mxv force= change in momentum/ time Velocity-time graphs distance= 0.5 x g x t^2 speed=v= g x t Velocity final (Vf) = Velocity initial (Vi) + gravity x time (gt)
Distance and Displacement
Distance is a scalar quantity (mentions magnitude and not direction) that refers to "how much ground an object has covered" during its motion. (measured in metres) Displacement is a vector quantity (mentions magnitude and direction) that refers to "how far out of place an object is"; it is the object's overall change in position. The diagram below shows the position of a cross-country skier at various times. At each of the indicated times, the skier turns around and reverses the direction of travel. In other words, the skier moves from A to B to C to D. Use the diagram to determine the resulting displacement and the distance traveled by the skier during these three minutes. Skier travels 180m in 1 minute rightwards to point B, then travels 140m in 1 minute leftwards to point C, and then travels 100m rightwards to point D Answer: Distance= 180m + 140m + 100m= 420m, Displacement= 140m rightwards.
Contrast and explain Distance and Displacement
Distance is a scalar quantity that measures "how much ground an object has covered" during its motion, whereas displacement is a vector quantity that measures the object's overall change in position. Distance has a magnitude, whereas displacement has a magnitude and direction. For example: If a man walks around a mall with a perimeter of 3 km, and reaches his original position, he has travelled 3 km, but has displaced 0 km. Another example is, if a marathon runner runs 200m in a marathon, then he travelled 200m, but has displaced 200m to the west.
Describe how strong structural unit shapes deform under load
Elastic materials and springs change shape when a force is put onto them. They stretch if you pull them and compress if you push them down with a load. These changes are called deformation. The greater the force, the greater the tension. Consequences are, if a shape can't handle the compression, it will buckle. If it can't handle the tension, it will break. You are able to tell this using Hooke's law, where the extension of a pulled object is directly proportional to the force applied to it.
Elasticity, Plasticity, elastic deformation, plastic deformation
Elasticity: measure of the amount that the object can return to its original shape after these external forces and pressures stop. Plasticity: when something is stretched and stays stretched, it is said to be plastic. Plastic deformation: Energy going into changing the shape of some material and it stays changed. Elastic deformation: When the material goes back to its original state.
Electromagnetic
Electromagnetism is the interaction of particles with an electric charge. Electric forces are produced by electric charges, attraction/repulsion between charges. Magnetic forces are produced only by moving charges, attraction/repulsion between poles. All of the light from the Sun and other sources consists of photons which are the electromagnetic force carriers. When small pieces of paper are attracted to a comb.
Ferromagnetism
Ferromagnetic metals, such as iron, have a strong tendency to form magnetic dipoles, meaning it exhibits strong magnetism in nature. Earth itself has a magnetic field due to the presence of iron. We can use electromagnetic fields to separate this type of metals, as magnets are materials that produce magnetic fields, which attract ferrous metals. Ferrous materials are the only objects that are physically attracted to magnetic fields. Because of this, electromagnetic fields can be used to extract ferrous metals from a mixture by placing a dipole or normal magnet close to that mixture or placing the mixture on a magnetic pulley, which will attract only ferrous materials.
Describe and explain the science behind the development of graphene as a material.
Graphene is a single layer of carbon that is bonded together in a repeating pattern of hexagons. Graphene is thinner than paper. Graphene's atoms are bonded closely together in a 2D layer. The atoms in graphene are flatly organized. Graphene has a crystalline structure; repeating and endless 3D structure. Graphene conducts electricity better than copper. Graphene is stronger by 200 times than steel and is lighter by 6 times. Graphene is nearly transparent since it absorbs 2% of light. It can boost internet speeds, extend the lives of computers and serve as a touch-sensitive coating. It is the strongest material in the world.
Gravity
Gravity is a natural phenomenon by which all objects with mass are brought towards each other including atoms, planets and even stars. The force that causes a ball you throw in the air to come down again. Matter attracts matter, it only attracts, weakest force, infinite range
Heliocentric and Geocentric
Heliocentric - the belief that the Sun is the centre of the solar system and the Earth revolves around the Sun. Geocentric - the belief that the Earth is the centre of the Universe and everything revolves around the Earth.
Useful fundamental forces
I think that electromagnetic force is the most useful force to mankind as it is of most help in day to day activities as they are used in fridges, cranes to make buildings and other structures and so on. While gravity does serve useful in the space sectors as many space flights use the gravity of other celestial bodies to act as a slingshot sort of thing to make the space flight move faster towards their goals.
Inertia
Inertia is the resistance of any physical object to any change in its state of motion. This includes changes to the object's speed, direction, or state of rest. Inertia is also defined as the tendency of objects to keep moving in a straight line at a constant velocity.
Laws of Moments
Law of moments: When an object is balanced (in equilibrium) the sum of the clockwise moments is equal to the sum of the anticlockwise moments. Force 1 (N) x its distance from the fulcrum (m) = Force 2 (N) x distance from the fulcrum (m) Torque or moment is given in 'Nm' = Newtons x Meters A moment is a "turning force". e.g : trying to open or close a door or using a see-saw The formula for calculating an moment is Moment (Nm) = force (N) x distance from fulcrum (in m) m ------------ f | d For example if a force of 1N is applied 4m away from the fulcrum the moment has a force of 4Nm. In order to balance the lever a force of 4Nm would have to be applied on the opposite side of the fulcrum. A 10N force placed 2m away from the fulcrum has a total force of 20 Nm and a 20N force placed 1m away from the fulcrum has a force of 20 Nm. The moments are balanced so the lever is too.
Magnification, magnify and resolution
Magnification - increase in apparent size of an image relative to the object's size Magnify - to make something appear larger than it is Resolution - the act of distinguishing between two separate but adjacent objects, sources of light between two nearly equal wavelengths.
Magnification and Resolution
Magnification is the process of enlarging the appearance of something without enlarging its actual size. Resolution is the act of distinguishing between two separate but adjacent objects or sources of light between two nearly equal wavelengths. A magnifying glass, in effect, tricks your eyes into seeing what isn't there. Light rays from the object enter the glass in parallel but are refracted by the lens so that they converge as they exit, and create a "virtual image" on the retina of your eye. This image appears to be larger than the object itself because of simple geometry: Your eyes trace the light rays back in straight lines to the virtual image, which is farther from your eyes than the object is and thus appears bigger.
Mass and weight
Mass is the amount of matter in an object. Roughly, the mass of an object is a measure of the amount of atoms in it. The basic measurement of mass is the kilogram. Mass is scalar as it has a magnitude but no direction. Weight is the force that acts on an object due to gravity and mass. It is measured in newtons (N) and is calculated through the formula W=mg, where W=weight, m=mass and g=gravity. Weight is a vector quantity since it has a size as well as a direction. The mass of an object never changes, however weight changes based on the object's mass and the gravitational field strength of the area. w ------ m | g f ------ m | g
What did Mendeeleev create? Differences between old and modern periodic table.
Mendeleev predicted the existence of eight new elements and proposed that some of the elements should have their atomic weight remeasured. In the modern periodic table, the elements are arranged in the order of increasing atomic number, whereas in Mendeleev's table they were ordered in order of increasing atomic weight. More elements have been discovered in the modern periodic table and there are no gaps in the modern periodic table.
Microscopes and what do they help us do?
Microscopes - Microscopes are optical instruments that are used to zoom into and enlarge objects that are very small and minute like bacteria. Microscopes can have either a single lens (simple microscope) or multiple lens (complex microscope) depending on the magnitude of magnification required. Microscopes have helped scientists understand and learn about cellular division in humans which made it possible to understand and prevent diseases. Microscopes have also helped examine tissues and blood to make further notes on diagnostics and various advancements in medical treatments.
Diamond and Graphite (Molecular structure, Hardness, Melting and boiling points, Electrical conductivity)
Molecular structure Diamond: Giant covalent structure, with each carbon covalently bonded to four other carbon atoms in a tetrahedral arrangement to form a rigid structure. Graphite: Giant covalent structure, with each carbon covalently bonded to three other carbon atoms in a hexagonal arrangement. Hardness Diamond: Extremely hard. Due to rigid, tetrahedral arrangement of carbon atoms. Graphite: Soft. Layers of hexagonally arranged carbon atoms can slide over one another, as the layers are held together by van der Waals forces of attraction. Melting and boiling points Diamond and graphite: Very high. A large amount of energy is required to break numerous, strong covalent bonds between carbon atoms. Electrical conductivity Diamond: Insulator. Mobile electrons are absent. All four valence electrons are used in covalent bonds. Graphite: Conductor. Three out of four valence electrons are used for covalent bonding with other carbon atoms. Remaining valence electrons can be delocalized across the planes of carbon atoms.
Newton's first law of motion in terms of inertia
Newton's first law of motion states that "An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force." Objects tend to "keep on doing what they're doing." In fact, it is the natural tendency of objects to resist changes in their state of motion. This tendency to resist changes in their state of motion is described as inertia. An object's inertia causes it to continue moving the way it is moving unless it is acted upon by an (unbalanced) force to change its motion. An unbalanced force is a net force.
Newton's law of universal gravitation
Newton's law of universal gravitation states that a particle attracts every other particle in the universe with a force which is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers. M1 and M2= the masses of the objects r= the distance between the two objects G= the universal gravitational constant of gravitation as is equal to 6.67x10^-11Nm^2kg^-2
Explain how forces change motion and so cause acceleration
Newton's second law says that when a constant force acts on a massive body, it causes it to accelerate, i.e., to change its velocity, at a constant rate. In the simplest case, a force applied to an object at rest causes it to accelerate in the direction of the force. However, if the object is already in motion, or if this situation is viewed from a moving inertial reference frame, that body might appear to speed up, slow down, or change direction depending on the direction of the force and the directions that the object and reference frame are moving relative to each other.
Newton's third law of motion
Newton's third law is: For every action, there is an equal and opposite reaction. The statement means that in every interaction, there is a pair of forces acting on the two interacting objects. The size of the forces on the first object equals the size of the force on the second object. The direction of the force on the first object is opposite to the direction of the force on the second object. Forces always come in pairs - equal and opposite action-reaction force pairs.
The principal constituents of our Solar System: Sun, rocky planets, gas planets, satellites, asteroids, comets, meteoroids
Planets: There are ten planets in the Solar System. Five of them are visible from Earth without using a telescope. Historically, the Sun, Moon and the five visible planets were used as the sources for the names for the seven days of the week. The Sun: The sun is a star, a hot ball of glowing gases at the heart of our solar system. Its influence extends far beyond the orbits of distant Neptune and Pluto. The temperature at the sun's core is about 27 million degrees Fahrenheit. Average diameter: 864,000 miles, about 109 times the size of the Earth. Rocky planets: A rocky planet is a planet that is composed primarily of silicate rocks or metals. Within the Solar System, the terrestrial planets are the inner planets closest to the Sun, i.e. Mercury, Venus, Earth, and Mars. Gas planets: A gas giant is a large planet composed mostly of gases, such as hydrogen and helium, with a relatively small rocky core. The gas giants of our solar system are Jupiter, Saturn, Uranus and Neptune. Satellites: Most of the planets have satellites. The satellite that revolves around the Earth is called the Moon. A satellite is an object that orbits a larger object in space. Asteroids: Asteroids are smaller than planets. They are small solid bodies composed of rock and debris that are found in the Asteroid Belt between Mars and Jupiter. Comets: Comets are objects consisting of frozen molecules of gases and other solid materials. The period of a comet refers to how long it takes the comet to revolve around the Sun. Some comets have very, very long periods. Meteoroids: A meteoroid is an interplanetary particle in the Solar System. When a meteoroid enters the Earth's atmosphere it heats up and evaporates producing a streak of light called a meteor. Sometimes they come in groups called meteor showers. If a meteor reaches the ground then it is called a meteorite. Dust: The inner Solar System contains a vast cloud of very small dust particles.
The properties of: protostars, main-sequence stars, red giants, white dwarfs, neutron stars, black holes
Protostar - A star begins its life as a cloud of gas, which is mostly hydrogen and helium. The particles experience a very weak attraction towards each other due to gravity.As the gas cloud becomes denser, the effect of gravity is to increase the pressure and temperature. As more gas is drawn in by the increasing gravity, the mass of the cloud increases and therefore so does its gravity.The increasing gravity compresses the gas further so that it becomes hotter and denser. It eventually becomes a protostar. Main-sequence star - A main sequence star is any star that is fusing hydrogen in its core and has a stable balance of outward pressure from core nuclear fusion and gravitational forces pushing inward. Red giants - A very large star of high luminosity and low surface temperature. Red giants are thought to be in a late stage of evolution when no hydrogen remains in the core to fuel nuclear fusion. White dwarf - A small very dense star that is typically the size of a planet. A white dwarf is formed when a low-mass star has exhausted all its central nuclear fuel and lost its outer layers as a planetary nebula. Neutron star - a celestial object of very small radius (typically 30 km) and very high density, composed predominantly of closely packed neutrons. Neutron stars are thought to form by the gravitational collapse of the remnant of a massive star after a supernova explosion, provided that the star is insufficiently massive to produce a black hole. Black hole - A black hole is a place in space where gravity pulls so much that even light can not get out. The gravity is so strong because matter has been squeezed into a tiny space. This can happen when a star is dying. Because no light can get out, people can't see black holes. They are invisible.
Red-shift
Red shift: When the light from distant galaxies have frequencies slightly lower than they should be - they are shifted towards the red end of the spectrum. The measurements of the red-shift suggest that all the galaxies are moving away from us very quickly. The more distant galaxies have greater redshifts than nearer ones. This means that more distant galaxies are moving away from us faster than nearer ones. This provides evidence that the whole Universe is expanding.
Resistive forces in gases and liquids
Resistance to motion - friction and drag When one object slides over another there is friction, a resistive force between the two surfaces. This arises because, on a microscopic scale, the surfaces are not completely smooth and the high points become stuck together. Air Resistance Air resistance (or drag), is a resistive force that acts against objects that are moving through the air. Drag acts on objects moving through any fluid (gas or liquid) - and is larger in liquids. Friction and drag forces: always act against the direction of motion are zero when there is no movement increase as the speed of the object increases. When the driving force is larger than the resistive force, the cyclist speeds up; when they are equal he travels at a steady speed, and when the driving force is less than the resistive force he slows down.
How is the universe structured?
The large-scale structure of the Universe is made up of voids and filaments, that can be broken down into: superclusters, clusters, galaxy groups, and subsequently into galaxies. At a relatively smaller scale galaxies are made up of stars and their constituents, our own Solar System being one of them.
Speed, Velocity and Acceleration
Speed is a scalar quantity that refers to "how fast or slow an object is moving." is the rate at which an object covers distance. Speed= Distance/Time Velocity is a vector quantity that refers to "the rate at which an object changes its position." Velocity is how fast or slow an objects moves in a certain direction. Velocity= Displacement/Time, Average Velocity= change in position/change in time, Average Velocity= final position - initial position/ final time - initial time Velocity final = Velocity initial + acceleration x time An object which moves in the negative direction has a negative velocity. If the object is speeding up then its acceleration vector is directed in the same direction as its motion (in this case, a negative acceleration). Example: A car traveling due east starts at position x = 5 meters. After 8 seconds, the car is at position x = 41 meters. What is the car's velocity? Answer: 41m - 5m= 36m east, 8s - 0s= 8s. 36m/8s= 4.5 m/s east Acceleration is a vector quantity and is the rate of change of velocity of an object with respect to time, where a change in velocity can be caused by a change in speed or in direction. It is measured in ms/2 or ms/^-2 or m/s/s. An object is accelerating if it is changing its velocity. Average Acceleration= change in velocity/ change in time, a= Vf - Vi / Tf - Ti, Vf= Velocity final, Vi= Velocity initial, Tf= Time final, Ti= Time initial
Contrast and explain the difference between speed and velocity
Speed, being a scalar quantity, is the rate at which an object covers distance. The average speed is the distance (a scalar quantity) per time ratio. Speed is ignorant of direction. On the other hand, velocity is a vector quantity; it is direction-aware. Velocity is the rate at which the position changes. The average velocity is the displacement or position change (a vector quantity) per time ratio.
Static electricity & Earthing
Static electricity is generated through transfer of electrons due to friction When two materials are rubbed together, electrons can be transferred from one to the other. It is always the electrons that are transferred. The object that gains electrons has an overall negative charge. The object that loses electrons has an overall positive charge. When an object becomes charged, such as a rod through friction, it gains or loses electrons from the object it was rubbed against and gains a charge. So in this case we assume that the rod gave away its electrons and became positively charged. If this positively charged rod were to come in contact with small bits of paper, it would attract the electrons in the paper towards the rod thus causing the paper to stick to the rod. Getting rid of a static charge in this way is called earthing.
Telescopes and what do they help us do?
Telescopes are optical instruments that are used to zoom into and enlarge objects that are distant to the eye Telescopes work by either using lenses to focus light (refracting telescopes) or mirrors to focus light (reflecting telescopes). Telescopes have helped mankind to explore the universe and identify geographical objects on the moon like mountains and craters. It has also helped scientists understand that light is emitted from the sun and other stars.
Outline the changes in displacement, velocity and acceleration for objects in free-fall
The changes in displacement, velocity and acceleration for objects in free-fall can be calculated with the formula, v= a*t and d=(a*t^2/2), where v= velocity, a= acceleration, t= time, d=displacement. Acceleration is= 9.81 m/s2 An object that falls through a vacuum is subjected to only one external force, the gravitational force, expressed as the weight of the object. An object that is moving only because of the action of gravity is said to be free falling and its motion is described by Newton's second law of motion.
Compass
The compass uses the magnetic field of earth so that the north side on the compass points to the north pole and the south side of the compass points to south. This was all invented back in 206 BC. Compasses are used mostly for navigation and coordination, usually by ships and aircrafts. You can also use it if you get lost in a forest, desert or mountain to see in what direction you are going and where going before.
Earth magnetic field
The earth has its own magnetic field, which behaves like a large dipole magnet or bar magnet through the centre of the planet which displays the same properties of a bar magnet.
SUVAT Equations
The equations of motion are known as the SUVAT equations. s - displacement (m) u - initial velocity (ms-1) v - final velocity (ms-1) a - acceleration (ms-2) t - time (s) A nail is fired from a nail gun into a fixed block of wood. The nail has a speed of 380 ms-1 just as it enters the wood. The nail comes to rest after penetrating 60mm into the wood. Find the time taken for the nail to come to rest. Assume that the retarding force on the nail is constant as it penetrates the wood. s= 60mm= 0.06m u= 380 ms-1 v= 0 ms-1 a=? t=? v2= u2 + 2as a= v2-u2/ 2s 0-(3802)/ 0.12m -144,400/0.12m a= -1203333 ms-2 v= u+at 0= 380 ms-1 + (-1203333 ms-2) x t -380 ms-1/ -1203333 ms-2)= t t= 0.0003157 s t= 3.157 x 10^-4 s
Strong Nuclear
The force is very short ranged. The strong force is the force that holds the nucleus of the atom together, even though other forces want to pull it apart. The electrostatic repulsion, part of the electromagnetic force, between the positive protons in the nucleus is very powerful.
Frictional forces
The frictional force is the force exerted by a surface as an object moves across it. It acts in the opposite direction of the object's motion. Friction results from the two surfaces being pressed together closely, causing intermolecular attractive forces between molecules of different surfaces. Air resistance is a force that is caused by the frictional forces of air acting on the object. It behaves in a similar way to regular frictional forces i.e it acts in the opposite direction of the object's motion. Frictional force is the force exerted by a surface as an object moves across it or makes an effort to move across. There are two types of friction forces; Static and sliding friction. it acts in the opposite direction of the object's motion. Friction results from the two surfaces being pressed together closely, causing intermolecular attractive forces between molecules of different surfaces. Intermolecular attractive forces are relatively weak forces that attract molecules of all types to each other. Friction depends on the attributes of the surfaces of the two objects and the angle at which they are pressed against each other.
Distance-time and Displacement-time graphs
The gradient of a Distance-time and Displacement-time graph gives the velocity.
Speed-time and Velocity-time graphs
The gradient of a Speed-time and Velocity-time graph gives the acceleration. The area under the line gives us the distance. Divide the area under the line into shapes and calculate the areas of the individual shapes and add them together to find the total distance travelled.
Significant figures
The number of significant figures in any answer should reflect the number of significant figures in the given data. That is to say, when dividing and multiplying, the number of significant figures must not exceed that of the least precise value. Ex: Find the speed of a car that travels 11.21 meters in 1.23 seconds. 11.21 / 1.23 = 9.11382114 The answer contains 9 significant figures. However, since the value for time in the question (1.23 s) is only 3 s.f., the answer should be can be written as 9.11 m/s add/sub - 1.26 (3 sig figs) + 2.3 (2 sig figs)= 3.56 = 3.6 rule: the answer has to be the number that has the lowest of numbers after the decimal point 1.26+102.3 (4 sig figs)= 103.56= 103.6 0.00700 - 3 sig figs ---- 0.052 - 2 sig figs -- don't count the zeroes until you find a non-zero number 370. - 3 sig figs ---- 10.0 - 3 sig figs ----- 705.001 - 6 sig figs -------- 37,000 - 2 sig figs -- non-zero digits and 0s in between numbers are significant leading zeroes are not significant trailing 0s with decimals count them as sig fig no demical don't count as a sig fig
Describe planetary orbits in terms of centripetal force and gravitational attraction
The planets travel around the sun in paths or orbits called ellipses. When an object moves in a circle its speed remains constant but as the direction is constantly changing so is its velocity. This is because velocity has size and direction whereas speed only has size. For an object moving in a circle a force is required to change the direction as defined by Newton's first law of motion. This force constantly pulls the object towards the centre of the circle. A force that pulls an object towards the centre of a circle is called centripetal force. The source for the centripetal force in the solar system is the gravitational force of the sun. Without the centripetal force from the sun, the planets would travel in a straight line. The velocity of the planets is high enough so that they continuously accelerate towards the sun without ever leaving their orbits. It is for this reason that the planets do not fall into the sun from its strong gravitational force of attraction. Gravity is the centripetal force that keeps planets moving around the Sun, and satellites moving around planets. A centripetal force is a net force that acts on an object to keep it moving along a circular path. The faster the object is moving, the bigger the centripetal force has to be to keep it moving in a circle. The heavier the object, the bigger the centripetal force has to be to keep it moving in a circle. A larger centripetal force is required to keep an object moving in a small circle because it has to change direction frequently.
The astronomical basis for the calendar: the day, the month, the year
The principal astronomical cycles are the day (based on the rotation of the Earth on its axis), the year (based on the revolution of the Earth around the Sun), and the month (based on the revolution of the Moon around the Earth).
Kepler's third law
The squares of the period of the planets are directly proportional to the cubes of the mean distances from the sun. (Law of Periods) K= R^3/T^2 K= Kepler's constant= 3.35 x 1018 m^3/s^2 R= Mean radius of orbit (m) T= Period of orbit (s) (the time it takes the planet to go around the Sun once)
Strength of force fields
The strength of force fields= 1/d^2 also known as the inverse square law states that everytime you move further away from the core of an object the weaker the strength of the force gets. Hence Field strength is indirectly proportional to distance.
Electroweak
The weak interaction is a very powerful force that acts on the scale of the atomic nucleus and plays a crucial role in powering stars and creating elements. Beta decay is an example of the weak force. During beta decay, a neutron disappears and is replaced by a proton, an electron and a neutrino.
State ratios of quantities as differences of orders of magnitude
To compare the size of an atom (10-10m) and proton (10-15m), subtract the size of the proton from the size of the atom 10^-10 - 10^-15 = 10^5 This means that an atom is 10^5 bigger than a proton
Interpret force systems in terms of strong structural unit shapes: cantilevers and right-angled triangles, arches and equilateral triangles
Triangles are used in bridges because they evenly distribute weight without changing their proportions. When force is applied on a shape like a rectangle it would flatten out. Before triangles were used in bridges, they were weak and could not be very big. To solve that problem engineers would put a post in the middle of a square and make it more sturdy. Equilateral triangles are most commonly used in truss bridges, while scalene triangles are commonly used in more modern designs. just about all bridges use right triangles. The strength of a bridge depends on a variety of factors, such as span, intended purpose and materials used. For centuries, bridges have been used effectively to close a gap between two areas. Today, bridges are used more often as a way of creating shorter commutes in congested areas, crossing waterways, railways and existing roads. It takes manpower, good physics and smart architecture to accomplish the task of designing and building a strong bridge. A beam bridge, simply explained, is piers on each end holding up a horizontal beam. Those piers anchor into the ground to keep the bridge in place. The closer the piers exist to each other, the stronger this type of bridge becomes and the more weight it can support. If the piers sit too far apart, the beam will not have adequate support, and the bridge could fail and collapse. For this reason, this type of bridge doesn't span more than 250 feet. Originally made out of wood, beam bridges are now made out of concrete, asphalt and steel.
Vector diagrams
Vector diagrams are diagrams that describe the direction and relative magnitude of a vector quantity through the use of vector arrows. It is similar to the force arrows mentioned above. Vector diagrams can describe the velocity of a moving object for example a car moving across a road.
Organize relevant information to formulate a testable hypothesis
When (independent variable) ______ is changed the (dependent variable) _______ will change by __________________________________, while keeping the (control variables) the same. This is because ___________________________________________________.
Describe Newton's second law of motion in terms of momentum
When an external force is applied on a body, its velocity changes, when the velocity of a body changes, then its momentum changes. If greater forces are applied on the body, then the change of velocity will increase in the given time, which will result in an increase in momentum of the body. This means the change in momentum is directly proportional to the external force applied on the body. Change in momentum= mv-mu Rate of change of momentum= (mv-mu) / t This means the rate of change of momentum is directly proportional to the external force applied on the body. (mv-mu) / t ∝ f, which is f ∝ (m(v-u)) / t, which leads to F ∝ m*a
Resultant forces
an object may have several different forces acting on it, which can have different strengths and directions. They can be added together to give the resultant force, which has the same effect on the object as all the individual forces acting together. A stationary object remains stationary if the sum of the forces acting upon it - resultant force - is zero. A moving object with a zero resultant force keeps moving at the same speed and in the same direction. If the resultant force acting on an object is not zero, a stationary object begins to accelerate in the same direction as the force. A moving object speeds up, slows down or changes direction.
Hooke's law
f=kx f= force in newtons (n) k= spring constant (n/m) x= distance from equilibrium (m)
How to calculate gravitational field strength
g=f/m f= force m= mass in kg g= gravitational field strength
Telescopes and Microscopes
human eye, magnifying glass, lab microscope, scanning electron microscope, astronomical telescope, hubble space telescope
Force of gravity between 2 objects
m1= mass of object 1 m2= mass of object 2 d = distance separating the objects centers G= 6.674 x 10^-11Nm^2/kg^2
Stopping distance
thinking distance+braking distance Factors that affect thinking distance - tiredness, drugs, alcohol Factors that affect breaking distance - the mass of the car, tyres, road surface and weather conditions
Static Equilibrium
when the forces acting on an object which is at rest are balanced, then the object is said to be in a state of static equilibrium