# SACE Stage 2 Physics Whole Course (WIP)

Flashcards by Ben Goetze, updated more than 1 year ago
 Created by Ben Goetze over 5 years ago
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### Description

Flashcards on SACE Stage 2 Physics Whole Course (WIP), created by Ben Goetze on 09/27/2015.

## Resource summary

 Question Answer For a projectile (in absence of air resistance) Horizontal Component of Velocity is constant Acceleration is in the vertical direction and is the same as that of a vertically free-falling object The time of flight of a projectile is determined by The change in vertical component of velocity and the acceleration The range of a projectile is calculated by multiplying the horizontal component of velocity and the time of flight. The maximum height of a projectile can be calculated from The vertical component of the initial velocity and the acceleration or the time of flight and the acceleration Air Resistance A resistive force that acts in the opposite direction to the velocity of a projectile at any instant The magnitude of the force of air resistance on an object depends on shape, size, speed and the surface texture and the density of the air The velocity of an object moving with uniform circular motion continually changes direction and hence accelerates. (The speed remains constant) The direction of the acceleration of an object undergoing UCM is towards the centre of the circle (centripetal) When a vehicle travels round a banked curve at the correct speed for the banking angle, the centripetal acceleration is caused by: The horizontal component of the normal force on the vehicle (not the frictional force on the tires) Newtons Law of Universal Gravitation Any two particles experience mutually attractive gravitational forces along the line joining them. The magnitude of these forces is directly proportional to the product o the masses and inversely proportional to the square of the distance between them. The centres of circular orbits of Earth satellites must coincide with the centre of the Earth because: For uniform circular motion to occur the only force acting should be a force inward (or down). If the centre of the circle does not coincide with the centre of the Earth, there will be a sideways component of the force acting, and so UCM cannot occur. Law of Conservation of Momentum In an isolated system (one where no unbalanced external forces act) the total momentum of the system remains the same regardless of any interactions between objects. Impulse The change in momentum Newtons Second Law in terms of momentum The net force is the rate of change of momentum with time. Coulomb's Law Any two stationary point charges experience mutual forces along the line joining them. These forces are attractive if the charges are unlike and repulsive if they are alike. The magnitude of these forces is directly proportional to the product of the two charges and inversely proportional to the square of the distance between them Principle of Superposition When more that two point charges are present, the force on any one of them is equal to the vector sum of the forces due to each of the other point charges Electric Field (Strength) The electric force per unit charge on a small positive test charge placed at a point, provided all charges remain undisturbed. Electric Potential Difference The work done per unit charge on a small positive test charge moved between two points. The magnitude of a magnetic field is the force per unit current element placed at right angles to the field, where a current element is the product of the current and its length. The direction of the magnetic force is perpendicular to the plane defined by I$$\Delta$$L. The main parts of a moving coil loudspeaker Cone, Magnet Structure, Voice Coil, Supporting Frame If a charged particle with charge q is moving with speed v at angle Theta to a magnetic field of strength B, then the formula for the force exerted on the charge is: F=qvB$$\sin\theta$$ If a charged particle enters a field with velocity at right angles to the field, its motion will be: Circular. Therefore $$\ F_c$$ = $$\ F_B$$ $$\left\{\frac{mv^2}{r}\right\}$$ = qvBsin$$\theta$$ r = $$\frac{mv}{qB}$$ In a cyclotron, the period of particles is constant and independant from speed since: Circumference: 2$$\pi$$r, one semicircle: $$\pi$$r t=$$\frac{\pi r}{v}$$= but r = $$\frac{mv}{qB}$$ v = $$\frac{rqB}{m}$$ Hence, T= $$\frac{2\pi m}{qB}$$ The speed of an electromagnetic wave is The speed of light The formula relating the frequency and wavelength of electromagnetic waves is c=f$$\lambda$$ The visible Light spectrum (colours and frequencies) ROYGBIV $$\ 7.5x10^{-7}$$ - $$\ 4x10^{-7}$$ m LADS A plane shoots a laser down (over the ocean) and some is reflected off the surface while some hits the bottom of the ocean and reflects. The time difference between the arrival times can be used to calculate the depth of the water. A strong laser is needed since light is scattered and absorbed Two sources of light are in phase if The crests and troughs are created/arrive at the same time. Coherent Waves Maintain constant phase relationship to each other. Hence they have the same frequency. Incandescent Source of Light A solid or liquid heated until it glows. Not all particles are vibrating with the same frequency. Hence not monochromatic or coherent. Interference When two or more waves overlap. When in phase they constructively interfere, wen out of phase they destructively interfere. That Path Difference things so we get p.d = dsin$$\theta$$ Write it out on some other program with diagram and paste it here later. Laser Speckle is produced by: Laser light being reflected off a rough surface and con/destructively interfering with itself. A laser can read information off a disc: The edge of the track/land is a 1, everything else is a 0. Since the track is $$\frac{1}{4} \lambda$$ deep, destructive interference occurs when it is at the border, and thus a dimming occurs. This is a 1, everywhere else is constructive interference and a 0. The laser is kept on track when reading a disc by: using 2 lasers that travel above and below the other as well as slightly in front and behind respectively. This means that they would normally always be on land. If the laser goes off track, one of these lasers will hit the track and change in intensity, signalling to the machine to correct the path. The energy and momentum of photons can be calculated using: E = $$\ hf$$ and p = $$\frac{h}{\lambda}$$ Photoelectric Effect When light of sufficiently high frequency is incident on matter, and is absorbed by the matter, causing the emission of electrons. The Stopping voltage for the photoelectric effect is: The minimum voltage at which the current reaches 0 in a photoelectric apparatus. Can be calculated using formula: $$\ E_{max} = e\Delta V$$ This is because the current will only reach 0 when the most energetic electron has been stopped. The work function of a surface The minimum energy required to remove an electron from it. In metals electrons exist in a range of energy levels, and the work function is the energy required to remove the most energetic electron The formula for the work function of a surface: $$\ W = hf_0$$, where W is the work function of a metal, h is planck's constant and $$\ f_0$$ is the threshhold frequency, or the minimum frequency that produces the effect X-rays can be produced using: An X-ray tube in which electrons are accelerated to high speeds (& hence energy), enter a heavy metal target and are slowed as they pass by positive nucleii. The loss of kinetic energy is accounted for in the release of a photon. X-rays produced using an X-ray tube exist in a continuous range of frequencies because: When being slowed by a nucleus, an electron can lose anywhere between none and all of its energy, and thus the photon produced can have any range of energies, up to the initial energy of the electron. The Attenuation of X-rays The degree of absorption of the X-rays by body tissues. The tenser the tissue, the thicker the tissue and the higher the atomic number of the elements present, the larger the attenuation. The penetrating power/hardness of X-rays Their ability to penetrate a substance. Hard X-rays have high penetrating power. Soft X-rays have low penetrating power. Matter wave Matter that behaves as a wave. Every particle has a matter wave associated with it. The De Broglie wavelength of a particle: $$\ \lambda = \frac{h}{p}$$ Electron Microscopes have a higher resolution than optical microscopes because: Waves do not reflect off objects that are smaller in size than the wavelength of the wave. Since electrons have a smaller De Broglie wavelength than photons, smaller objects can be observed The Emission Spectrum of an Element A specific set of wavelengths released by an atom because electrons have become excited and jumped up energy levels, and then dropped back down, releasing the energy corresponding to the difference between the levels as a photon. Due to the different number of protons in each elements nucleus, each element has unique energy levels and hence a unique emission spectrum. The emission spectrum of Hydrogen in the visible spectrum has __ lines. 4 Series of Hydrogen Emission Spectrum Balmer- Visible spectrum into ultraviolet spectrum Lyman - ultraviolet spectrum Paschen- Infra-red region Series Limit The transition between the zero energy level and the appropriate energy level for that series, e.g Paschen - 3, Balmer - 2, Lyman - 1. Fun Acronym to remember the order: gotta Love BP (yes the oil company) Ionisation Energy The minimum energy required to remove an electron from an atom (to ionise it) Absorption Spectrum If white light is passed thorugh a vapourised element, it will absorb those frequencies with energies corresponding to the energy difference between levels. These will be the same frequencies as it emits. This is the absorption spectrum. Meta Stable State An excited state in which an electron/atom is able to exist for an extended period of time. Flourescence When an electron de-excites (often from a meta-stable state) and releases several low energy photons rather than one high energy photon Stimulated Emission When a photon with energy corresponding to the energy difference between a level inhabited by an electron and a lower level interacts with that electron and causes it to transition between these levels, releasing a photon identical to the original one. Photons produced in Stimulated Emission are identical in which aspects: All: energy, direction of travel and phase. Population Inversion Where there are more atoms in a meta-stable excited state than in a lower state (such as the ground state). In this case there would be more stimulated emissions than absorptions of the radiation emitted. Main components of a Helium-Neon gas laser: The active medium: the helium and neon gas The pump: discharges electrons though the tube to excite helium atoms. These then collide with neon, passing on their energy and putting the neon in a meta-stable state allowing population inversion to occur. Mirrors at either end: to reflect the laser, and then when it reaches high enough intensity let some through (the laser) and reflect the rest Attributes of Laser Light High Intensity, Monochromatic, uni-directional (almost) and coherent Applications of Lasers LADS (Laser Airborne Depth Sounder) Disc Reading Welding/Cutting Medicine Nucleii consist of Protons and Neutrons Atomic Number Z. Number of Protons Mass Number A. Total number of nucleus The nucleon force/strong nuclear force The strong, short range attractive force experienced by nucleons. Isotopes Atoms that contain the same number of protons but different number of neutrons Formula for calculating the energy involved in creating or destroying a nucleus $\ E = mc^2$ Binding Energy The minimum energy necessary to separate a nucleus into its constituent nucleons Things conserved in nuclear reactions Total Charge Total number of nucleons momentum mass-energy or total energy if $$\ m_{reactant} > m_{product}$$ Energy is released if $$\ m_{product} > m_{reactant}$$ Energy is Absorbed In a nuclear reaction, the less massive the particle produced: The more momentum and kinetic energy it will have Radioisotopes can be produced by: firing protons or deuterons at an atom Flourine/Oxygen - 18 Used in PET Scans All elements with atomic number greater than ____ decay radiactively 83 As the size of the nucleii increase, the ratio of protons:neutrons _________ to: decreases, to counter the increasing repulsive force between the protons Alpha Decay Where an alpha particle ( $$\ He_2^4$$) is emitted by the nucleus on decay Alpha particles have high/low binding energy? High. The alpha particle released in alpha decay have specific energies because: Nucleii have discrete energy levels/states. Depending on the state of the nucleus after reactions changes the energy received by the alpha particle. In all nuclear decays a _______ ______ is released Gamma ray (photon) Beta Minus Decay A beta minus particle ( $$\ e_{-1}^0$$ ) is released by nucleus Beta minus decay occurs when an atom has excess neutrons: $$\ n_0^1 \xrightarrow\ p_1^1 + e_{-1}^0$$ Beta particles are released with a continuous range of kinetic energies because: Anti-neutrinos are emitted $$\overline {v}$$, and the kinetic energies are split between these randomly Beta Plus Decay A beta plus particle is released $$\ e_{+1}^0$$ by the nucleus on decay Beta Plus Decay occurs when: It occurs when an atom has excess protons $$\ p_1^1 \xrightarrow\ n_0^1 + e_{+1}^0$$ In a beta plus decay, a ________ is emitted: a neutrino (v) is emitted Particles/Antiparticles Opposites of each other e.g positrons, electrons. When particles and anti particles meet they annihilate each other, converting their mass into energy (gamma ray photons) e.g. $$\ e_{+1}^0 + e_{-1}^0 \xrightarrow\ \gamma_0^0 + \gamma_0^0$$ Ionising Ability the number of ionisations caused per unit travel. In ionising ability: $$\alpha > \beta > \gamma$$ Radiation in penetration through matter $$\alpha < \beta < \gamma$$ Ionising Radiations Radiation that can cause ionisation events in matter (knock out electrons) Types of ionising radiation: alpha, beta, gamma, ultra-violet, x-ray, neutrons and protons Ionising Radiation can stem from: Radioactive materials in Earth, cosmic radiation e.g. high energy photons, neutron, protons and other charged particles emitted by the sun during solar flares. Ionising radiation can: break chemical bonds in living matter, changing its composition and thus killing, mutating cells and can cause genetic defects in birth, or cancer Exposure to Ionising Radiation can be decreased by: increasing distance from the source, reducing exposure time or shielding Half Life The time required for $$\frac{1}{2}$$ of a radioactive sample to decay Formula for number of nucleii remaining in radioactive decay: $$\ N = \frac{N_0}{2^n}$$ The Activity of A Radioactive isotope The number of nucleii that decay per unit time (Bq) A PET Scanner is able to detect sites such as cancer because: Active sites such as cancer will absorb lots of radioisotope and thus produce many gamma rays, due to $$\ \beta ^+$$ decay causing annihilation events with electrons at the site Nuclear Fission A process in which a very heavy nucleus splits into two lighter nucleii. Some elements such as Thorium and Plutonium undergo this process spontaneously Fission can be induced using A low energy neutron The neutron used to induce fission must be low energy because A high energy neutron tends to collide and recoil from a nucleus, while a low energy neutron is absorbed. The absorption of the neutron into the nucleus causes fission because When the neutron enters the nucleus,it distorts its shape and causes it to vibrate in an elongated way. Because of this the strong nuclear force is no longer able to counteract the coulombic repulsion between protons and so the nucleus splits When fission occurs, _______ _______ are usually produced several neutrons Moderator a substance of low mass that does not readily absorb neutrons. A moderator is necessary in a fission reactor because: the neutrons produced have far too high energy, and must be slowed. By colliding them with the moderator particles, they lose kinetic energy, and can then be used to cause further fission events. To sustain a chain reaction: Each fission event must cause at least one more fission event. Core The whole container in which the nuclear fission takes place Fuel Rod A rod of enriched Uranium 235 Moderator A substance such as water under high pressure (or heavy water) Control Rod Rods of material that absorb neutrons well e.g. Boron or Cadmium. They are interspersed between fuel rods and can be raised or lowered to control the rate of reaction Heat Exchanger Coolant in the core is heated by energy released from the fission, and then moves to the heat exchanger where it heats water to produce steam Safety Rods Control Rods that can be quickly dropped into the reactor to stop the reaction if necessary Shielding A thick steel/concrete layer to stop radiation produced by the reactor The only force acting on a body projected into free flight near the surface of the Earth (neglecting air resistance) is: The formula for calculated this force is: The force due to gravity $$\ F=mg$$ The magnitude of the force due to gravity near the surface of the Earth is: $$\ 9.8 ms^{-2}$$ The velocity of a projectile is at a ______ to its motion at all times tangent The vertical component of velocity of a projectile can be found with equation: $$\ v = v_0 + at$$ Velocity of a projectile can be split into components using equations: $$\ v_x = vcos\theta$$ $$\ v_y = vsin\theta$$ The maximum height above launch of a projectile can be calculated using equations: $$\ v_y^2 - u_y^2 = 2a_ys_y$$ This is because at maximum height $$\ v_y$$ is 0 The range of a projectile can be calculated using equation: $$\ Range = u_xt$$ The angle that achieves the maximum range for projectiles launched from ground height: 45 degrees Two projectiles launched from ground height with same speed but different launch angles will achieve the same range if: The launch angles add to 90 degrees For a projectile with given speed and launch angle, the higher the launch height: The larger the range As the launch height increases, the optimum angle: decreases from 45 degrees The optimum launch angle to achieve maximum range decreases as launch height increases because: The projectile spends more time on its downward path and thus increasing the magnitude of the horizontal velocity yields greater rangers (it more than compensates for any loss of distance due to less height achieved) For an object undergoing UCM its' _________ remains the same but its ___________ is constantly changing Speed, Velocity Acceleration is defined as The rate of change of velocity with respect to time The period of rotation The time taken to complete one revolution and is given by formula $$\ T = \frac{2\pir}{v}$$ The formula for the force causing centripetal acceleration $$\ F = ma_c = \frac{mv_2}{r}$$ Newtons Law of Universal Gravitation Equation $$\ F = \frac{Gm_1m_2}{r^2}$$ Geostationary Satellite A satellite that remains directly above the Earth's surface throughout its life the formula for calculating momentum $$\ p = mv$$

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