EDEXCEL KEY CONCEPTS OF PHYSICS

1. Common names SI units are used all round the World. Derived units with special names SI Units for physical quantities Multiples and sub-multiples of units EDEXCEL KEY CONCEPTS OF PHYSICS Conversion between units Standard form Significant figures Remember in any calculation you should round down to the lowest number of significant figures given. e.g. 0.33566 to 2 s.f. = 0.34 (2 s.f.) The second and third significant figures come straight after the first, even if they are zeros. The first significant figure of a number is the first digit that is not a zero. Remember to write down how many significant figures you have rounded your answer to.

2. Acceleration is negative, object is decelerating a = (v – u) ÷ t Acceleration is positive, object is accelerating s = d ÷ t Speed is rarely constant. Average speed = distance ÷ time Equations Scalar and vector quantities Measuring Motion Describing Motion Acceleration in free fall = 10m/s2 EDEXCEL TOPIC 2 - MOTION AND FORCES (part 1) Motion Graphs Distance-time graphs Velocity-time graphs

3. An object travelling in a circle at a constant speed, is constantly changing direction so it is constantly changing velocity which means it is accelerating. Each Kg has a gravitational pull of 9.8N. There must be a resultant force acting upon the object. Object moves left with a force of 5N. W = m X g Weight = mass X gravitational field strength HIGHER ONLY Contact and Resultant forces Forces Reactions and stopping EDEXCEL TOPIC 2 - MOTION AND FORCES (part 2) HIGHER ONLY Newton’s Laws and Momentum . An alert driver has a reaction time of 1s. Frictional forces decelerate a moving object and bring it to rest. Frictional forces decelerate a moving object and bring it to rest. Force = mass X acceleration. Car’s mass 1000Kg, single decker bus 10,000Kg, loaded lorry 30,000Kg F = m X a Speed affects both thinking and braking distances. PHYSICS ONLY Speed increases so does stopping distance. Speed increases thinking distance also increases at the same rate. F = (mv – mu) ÷ t Is a vector. Momentum = mass X velocity Force = change in momentum ÷ time. Crumple zones Momentum If speed doubles, braking distance increases by a factor of four (22). p = m X v HIGHER ONLY Work done to bring a vehicle to rest = its initial kinetic energy

4. Conduction transfers thermal energy through solid objects. Total energy input = useful energy output + wasted energy Energy is only useful when it is transferred from one store to another useful store In buildings the lower the thermal conductivity the slower the rate of energy transfer Energy transfers Conservation of energy EDEXCEL TOPIC 3 - CONSERVATION OF ENERGY (PART 1) Efficiency Efficiency can be increased by reducing the thermal energy transferred due to friction by lubricating and the energy transferred by heating by insulation. Efficiency = Useful output energy transfer Total input energy transfer HIGHER ONLY Efficiency = Useful power output Total power input

5. Oil spillages cause serious marine environmental problems Nuclear waste is dangerous and difficult to dispose of and there is always a risk of catastrophes. Burning coal and oil release sulphur dioxide which causes acid rain. CO2 is a greenhouse gas and contributes to global warming Energy resources are chosen for their effect upon the environment. Trends in Energy resource use Fossil fuels have a negative effect upon the environment. EDEXCEL TOPIC 3 - CONSERVATION OF ENERGY (PART 2) Targets have been introduced to reduce the use of fossil fuels. Car companies are designing electric and hybrid cars. Hybrid cars and solar panels for houses are still very expensive Energy resources Research into improving the reliability of renewable energy resources is expensive and takes time. People object to wind farms (visual pollution). Do not provide a lot of energy and some are unreliable Most do cause some damage to the environment but less than non-renewables

6. Sound waves travelling through different mediums, the frequency stay constant. Equations Basics of waves Measuring waves EDEXCEL TOPIC 4 - WAVES Waves change speed due to the different density of mediums. Speed of Light = 3 x 108 m/s Properties of waves Speed of sound = 340m/s If the waves goes from a thinner medium to a thicker medium, (e.g. air to glass), it will slow down. HIGHER ONLY PHSICS HIGHER ONLY Waves travel through different medium at different speeds Speed of waves in water depends upon depth If the waves goes from a thicker medium to a thinner medium, (e.g. glass to air), it will quicken up. What actually happens to a wave depends upon it’s wavelength and the property of the material involved. From deep water to shallow water, speed slows down You must know how sound travels through the ear. Sound waves travel at different speeds in different media. Sound waves travel faster in solids, than liquids than gases. Air Water Frequency does not change but wavelength does (v = f Wavelength increases as speed increases, if speed slows down, wavelength get shorter. PHSICS HIGHER ONLY PHSICS ONLY

7. He split sunlight into a spectrum using a prism. He put a thermometer in each temperature and measured the temperature just beyond the red end of the spectrum He found the red end was hot but just beyond the red end was even hotter. Light refracts as it slows down in a denser substance. Radio waves absorbed by metal and cause oscillations in electrical circuits connected to the aerial. Metal can be used as an aerial to receive radio waves. More absorbed, temperature increases. Temperature of Earth is controlled by the amount absorbed = amount radiated. Radio waves made by oscillations in electrical circuits. For a body to be at constant temperature, the amount absorbed = amount radiated. Angle of incidence = angle of reflection(i) = (r) EDEXCEL TOPIC 5 LIGHT AND EMS Electromagnetic Spectrum Different EM wavelengths travel at different velocities through different materials. EM waves are generated by changes in atoms and nuclei giving large range of frequencies. Light HIGHER ONLY Different substances absorb, transmit, refract and reflect EM waves depending upon wavelength. e.g. changes in the nucleus of an atom creates gamma rays. Visible light is often produced by changes in an electron’s energy level. The more powerful the lens, the more the rays of light refract so the shorted the focal length. EM waves transfer energy from source to observer e.g. infrared waves transfer energy from heater to person Our eyes only detect a small part of spectrum e.g. visible light. Short wavelengths, high frequency and high energy. Long wavelengths, low frequency and less energy. Focal length is linked to the power of lens. Power of lens increases with its curvature. Frequency increases. Object close to a converging lens will form a virtual image The image appears to be on the same side as the object.

8. Radioactivity Revision Worksheet Complete the table about subatomic particles: Explain how a Geiger-Müller tube works: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………… Draw and label a diagram of J.J. Thomson’s Plum Pudding Model: Describe what each of the types of radiation is: State the number of protons, neutrons and electrons in one atom of the following element: Describe what Ernest Rutherford found when he fired alpha particles at gold foil: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………… Protons: ……… Neutrons: ……… Electrons: ……… An atom of fluorine has 9electrons. Draw an electronconfiguration diagram forthis element: How did Rutherford’s findings change our understanding of the atom: …………………………………………………………………………………………………………………………………………………………………………………… Compare the ionising properties of alpha, beta and gamma radiation: …………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………… Explain what happens when a neon atom absorbs energy: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………… Label the diagram of an atom: What can be used to stop the following: List 5 types of background radiation: 1. 4. 2. 5. 3. Match up the following: Define the following: Atomic Mass- Atomic Number- Isotope- How is photographic film used to detect radiation? ……………………………………………………………………………………………………………………………………………………………………………………

9. CP6 Revision Worksheet Rate each of the learning outcomes for how you feel about them: Radium-226 emits an alpha particle. What is the other product? Iodine-131 undergoes ß- decay. What is the other product? CP6.1 Describe the structure of an atom (in terms of nucleus and electrons). CP6.1 State where most of the mass of an atom is found. CP6.2 State the sixes of atoms and small molecules. CP6.17 Describe an early model of the atom. CP6.17 Describe how an why our model of the atom has changed over time, including the plum pudding model and the Rutherford alpha particle scattering. CP6.3 State what is meant by an isotope. CP6.3 Represent isotopes using symbols. CP6.2 State the sixes of atoms and small molecules. CP6.3/CP6.4 Explain how atoms of different elements are different (in terms of numbers of electrons and protons). CP6.5 Recall the charges and relative masses of the three subatomic particles. CP6.6 Explain why all atoms have no overall charge. CP6.7 Describe where electrons are found inside atoms. CP6.8 Describe when electrons can change orbit. CP6.9 Recall what an ion is. CP6.9 Describe how ionisation occurs. CP6.17 Describe some of the evidence for the Bohr model of the atom. CP6.12 Explain what background radiation is. CP6.12 & CP6.14 Describe how radiation measurement need to be corrected for background radiation. CP6.13 List some sources of background radiation. CP6.14 Describe how photographic film can be used to detect radioactivity. CP6.14 Describe how a Geiger-Muller tube works. CP6.14 Describe how the amount of radioactivity can be measured (in terms of the darkness of photographic film or by attaching a counter to a GM tube). CP6.10 List five types of radiation that are emitted in random processes from unstable nuclei. CP6.11 State that the five types of radiation are ionising radiations. CP6.15 Describe what alpha and beta particles are CP6.15 Describe the nature of gamma radiation. CP6.16 Compare the penetrating abilities of alpha, beta and gamma radiation. CP6.16 Compare the ionising abilities of alpha, beta and gamma radiation. CP6.18 Describe the process of β- decay. CP6.19 Describe the process of β+ decay. CP6.20 Explain how the proton and mass numbers are affected by different kinds of radioactive decay. CP6.21 Describe what happens during nuclear rearrangement after radioactive decay. CP6.22 Balance nuclear equations for mass and charge. CP6.23 Describe how the activity of a substance changes over time. CP6.23 state how half-life can be used to describe the changing activity of a substance. CP6.20 Recall the unit for activity. CP6.25 & CP6.26 Describe how half-life can be used to work out how much of a substance will decay in a certain time. CP6.27 Carry out calculations involving half-life. CP6.29 Describe the hazards of ionising radiation in terms of tissue damage and possible mutations. CP6.31 Explain the precautions taken to reduce the risks from radiation and ensure the safety of patients exposed to radiation. CP6.31 Explain the precautions taken to reduce the risks from radiation and protect people who work with radiation. CP6.32 Describe the differences between contamination and irradiation effects. CP6.32 Compare the hazards of contamination and irradiation. Describe what half life means: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………… What is the half life of the following radioactive substance: Describe and explain how radioactive sources should be handled safely: ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

10. Pushing an object along a rough surface and work is done against frictional forces. Energy is transferred to the kinetic energy store of the object as it starts to move. Some energy is also transferred to the thermal energy store of the object, the surface and the surroundings due to friction. The temperature of the object and surroundings increases. Energy transfer = Work done ΔGPE = m X g X Δh Energy transfer involves the way energy is stored when systems change Work done = force X distance moved in the direction of the force Change in Gravitational Potential Energy = mass X gravitational field strength X change in height. E = F X d Work Kinetic Energy = ½ X mass X velocity2 Total energy remains the same (No net change). KE = ½ X m X v2 EDEXCEL Topic 8 ENERGY – FORCES DOING WORK Power Power = Work done ÷ time P = E ÷ t Efficiency = useful energy transferred by the device ÷ total energy used by the device.

11. Vector diagrams Objects affecting each other The sum of clockwise moments = The sum of anti-clockwise moments . EDEXCEL TOPIC 9 - FORCES AND THEIR EFFECTS Rotational forces Moment of a force = force X distance normal to the direction of the force. The wheel with more teeth turns slower but the moment of the turning force will be bigger. Gear A has 12 teeth and gear B has 18 teeth. Ratio of moments = ratio of teeth = ratio of radii.

12. The further apart the objects, the weaker the force. A non-contact force. Static dischargers are used on planes to remove charge. Dangers Insulators can be charged by friction. Charges and static EDEXCEL TOPIC 11 – STATIC ELECTRICITY. PHYSICS ONLY Uses Electric fields Rubbing a balloon causes transfer of electrons to balloon due to friction. Balloon is now negatively charged. Balloon moves towards wall. Charges in wall separate due to negative charges on balloon repelling negative charges in wall surface. Leaving positive charges in wall surface attracting negatively charged balloon.

13. Fields from individual coils cancel out to give a weaker field outside the solenoid. Fields from individual coils add together to form an almost uniform filed along the centre of solenoid. If current and magnetic field are parallel to each other , no force on wire. A compass or iron filings placed near the wire, will show the direction of the magnetic field. They exert equal and opposite forces on each other. Split –ring commutator makes sure current always flows in correct direction to make coil spin. Electromagnetism When current flows through a wire, a concentric magnetic field is created. EDEXCEL TOPIC 12 MAGNETISM AND THE MOTOR EFFECT Magnetic forces Force on a conductor at right angles to a magnetic field carrying a current = magnetic flux density X current X length. Magnets and magnetic fields Magnetic elements are Nickle, Iron and Cobalt.

14. Alternating current in the primary coil creates a magnetic field, which is constantly changing. The magnetic field is carried to the secondary coil by The iron core. The National Grid Electromagnetic induction The magnetic field induces a changing potential difference in the secondary coil. Reversing the magnetic field, reverses the direction of the induced p.d. EDEXCEL TOPIC 13 ELECTROMAGENIC INDUCTION A changing magnetic field can induce a p.d. in a wire. Current then flows. A coil is used so there is more wire in the changing magnetic field. VP÷ VS = NP ÷ NS Rotating electromagnetic surrounded by coils of wire. Potential difference across primary coil ÷ Potential difference across secondary coil = Number of turns on primary coil ÷Number of turns on secondary coil Transformers and energy Large scale generators work in the same way in power stations. Potential difference across primary coil X current in primary coil = Potential difference across secondary coil X current in secondary coil VP X IP= VSX IS Transmitting power at high voltage is more efficient Use these questions to prove this. Power = Energy transferred ÷ time taken Electrical Power = Current X Potential difference Power = Current squared X Resistance

15. P = m ÷ V Density = mass ÷ volume. Calculate pressure of volume of gases of a fixed mass at a constant temperature. Particles and density P1V1 = P2V2 EDEXCEL Topic 14 PARTICLE MODEL Reducing the volume of a gas at a fixed temperature, increases pressure. (Less space so particles collisions occur more frequently and with more force). Change in thermal energy = mass X specific heat capacity X temperature change. ∆E= m X cX ∆θ Temperature, pressure and Volume Decrease pressure, gases are expanded. To reduce thermal transfer, (make more accurate) use insulation. Increase pressure, gases are compressed. Energy and Changes of state Pressure is a net force per unit area, when particles collide a pressure is exerted. When particles collide with a surface, a force is exerted. This is a resultant force at right angles to the surface. Convert between kelvin and Celsius +273. Convert between Celsius and kelvin -273. Energy needed = mass X specific latent heat. ∆E= m X L Gas particles are in a constant state of random motion.

16. More than one force is needed to bend, stretch or compress an object. Diagonal line through 0,0 = directly proportional. Diagonal line = proportional. Forces are needed to change the shape of an object. Forces and elasticity Extension and energy transfers Force exerted on a spring = spring constant X extension. F = k X x Work done on a spring = ½ X spring constant X extension2. EDEXCEL Topic 15 FORCE AND MATTER E = ½ X k X x2 Work done can also be calculated by working out th4e area under a force-extension graph. Pressure in fluids causes a force normal to a surface. Pressure = force normal to surface ÷area of surface Pressure P = F ÷A Pressure due to a column of liquid = height of the column X density of liquid X gravitational field strength. P = h X p X g B A C