10th Grade Physics Units
Knowledge and understanding 10th grade Physics course 2012 K and U
Data and formula sheet: Formula sheet
What is physics?
Assessment: crit DE Helicopters investigation, Notes about lab reports
Quantities are measured within a system of units.
The SI system uses the metre, second and kilogram as base units.
Derived units such as metres per second and Joules are made up from base units.
Unit prefixes including micro, milli, centi, kilo, mega, giga are used to modify the size of units.
Conversion between units involves multiplying by a power of 10.
Scientific notation such as 3×108 is easier for very large or small quantities.
Estimation techniques can be used to verify the answer from a particular calculation.
Physical measurements are made using instruments which measure to a particular level of accuracy.
Standard error can be quoted as a plus or minus value.
Random errors are due to the inaccuracy of measurements
Systematic error
Reliability
Validity
Investigation skills include planning a fair test, writing a hypothesis, drawing tables and graphs, and writing conclusions and evaluations.
Calculations should be set out with known quantities, the relevant formula, substitutions and a clear answer with a unit.
Physicists carry out thought experiments to help them conceptualize problems.
Flight
Assessment: crit AB Flight essay
Velocity and Acceleration
Velocity is a vector quantity and measures the speed of an object in a particular direction.
An object with no resultant force has a constant velocity. (Newton’s first law of motion)
Acceleration is the change in velocity of an object (which can be a change in speed and/or direction) and is calculated using a = ∆v/t
Equations of motion with constant acceleration
Displacement is a vector which represents the distance and direction.
Velocity is speed in a particular direction and is a vector quantity.
Acceleration is the rate of change of velocity.
uvast equations are used to solve kinematics problems of motion in one dimension where the acceleration is constant. u represents the initial velocity in m/s, v the final velocity in m/s, a the acceleration in m/s2, t the time, and s the displacement.
v = u + at s = ut + 1/2at2 s = ½ (u + v)t v2 = u2 + 2as
Force and acceleration
Forces can cause a change in the shape of an object, or an acceleration which can be calculated using F = ma (Newton’s second law of motion)
Mass and Weight
The mass of an object is the ‘quantity of matter’ and is given in kg.
The weight of an object is the gravitational force in Newtons. The weight changes depending on the gravitational field strength (g) and can be calculated from
W = mg.
The gravitational field strength near the surface of the Earth, g = 9.8N/kg
Freefall
Objects in freefall accelerate towards the Earth with constant acceleration.
Air resistance increases with velocity. The terminal velocity occurs when the forces of air resistance and weight are balanced and there is no acceleration.
Forces
Force diagrams represent the forces acting on one object exerted by other interacting objects.
Each force is represented by an arrow with the length of the arrow showing the magnitude of the force.
The resultant force on an object can cause acceleration, rotation or a change in shape.
Newton’s laws of motion are used to determine the motion of an object when forces are exerted on it.
Density
The density of an object is given by r = m/V where r is the density in kgm-3, m is the mass in kg and V is the volume in m3.
Buoyancy
An object in fluid will experience an upthrust force equal to the weight of the fluid it displaces.
Energy and Power
Assessment: crit AB Energy crisis essay (Example geothermal essay) crit DE Rate of cooling investigation
Energy
Energy can take different forms including kinetic, potential (chemical, nuclear, electrical, gravitational, elastic), thermal, and radiant.
Energy can be transferred (from one object to another) or transformed (to a different type).
Energy transfer diagrams show the transfer and transformation of energy.
The total amount of energy in a closed system is constant. (law of conservation of energy).
The unit of energy is the Joule (J). Energy is calculated in different ways for each form of energy.
Work
When energy is transformed or transferred, work is done.
Work = Force x distance W = F x d
The unit of work is Joules.
Efficiency
Energy transformation processes are not usually 100% efficient, and often energy is dissipated as heat when energy is transferred or transformed.
efficiency = energy output ÷ energy input
efficiency = power output ÷ power input
Efficiency can be expressed as a fraction, or as a decimal between 0 and 1, or as a percentage.
Power
Power is the rate of energy transfer and is the energy transferred in one second.
Power = Energy change ÷ time, P = E/t
The unit of power is Watts 
Kinetic Energy
The kinetic energy in Joules is calculated by Ek = ½mv2 where m is the mass of the object in kg and v is its velocity in ms-1
Gravitational Potential Energy
The gravitiational potential energy is calculated by Ep = mgh where m is the mass of the object lifted through a height h in a gravitational field of field strength g
At the Earth’s surface, g= 9.8ms-2
Elastic Potential Energy
The elastic potential energy of a compressed or stretched object is E = ½ke2 where k is the spring constant and e is the extension of the object from its equilibrium position
Thermal Energy
The change in thermal energy and temperature rise are related by the equation E = mcDT where E is the change in thermal energy, m is the mass of the substance and DT is the temperature change.
The specific heat capacity, c, of a material is the energy needed to raise the temperature of 1kg by 1Kelvin (or 1oC).
The units of specific heat capacity are Joules per kilogram per Kelvin (J/kg/K)
Temperature
The particle theory of solids, liquids and gases explains many of the macroscopic properties of matter.
The temperature of an object is given by the average kinetic energy of its particles.
Two objects in thermal equilibrium (at the same temperature) have particles with the same average kinetic energy.
When two objects at different temperatures are in contact, energy is transferred from the higher temperature object to the lower temperature object.
The internal energy of an object is the total kinetic and potential energies of the particles. (U=PE + KE)
Phase changes between different states of matter cause changes to the potential energy of the particles of a substance.
Absolute zero is the temperature at which the particles of a substance have no kinetic energy. This occurs at -273.15°C. The Kelvin scale of temperature is defined by absolute zero and is designed so that 1 Kelvin = 1°C. This gives absolute zero (0K) as -273.15°C.
Heat Transfer
When heat is transferred to an object, its internal energy can change and/or it can do work on its surroundings.
Heat energy is transferred by conduction, convection and radiation.
Conduction involves heat transfer between two objects in contact.
Convection involves heat transfer by convection currents in fluids (liquids and gases).
Radiation involves heat transfer by electromagnetic waves. The frequency of radiation increases with increasing temperature.
Power stations
Thermal power stations are used to generate electricity from a source of heat. The heat may be produced by burning fuel, nuclear reactions or geothermal energy.
A thermal power station contains a boiler, turbine, generator (alternator) and transformer.
Energy resources can be renewable or non-renewable. Non-renewable resources (such as fossil fuels and uranium) are finite and will run out. Renewable resources (such as wind and solar) will not run out.
Different methods of generating electricity have different advantages and disadvantages including those related to generating capacity (power output), availability of resources, reliability of supply, safety and environmental impact.
EM Waves
Assessment: crit AB Detection and imaging using EM waves essay
Wave properties
A wave transfers energy (but not matter) through a medium. Electromagnetic waves can transfer energy through a vacuum.
The frequency of a wave is the number of oscillations of a point per second, measured in Hertz.
The wavelength of a wave is measured from one point on a wave to an equivalent point on the next wave.
In a transverse wave, the vibrations are at right angles to the direction of motion of the wave.
In a longitudinal (compressional) wave, the vibrations are in the same direction as the motion of the wave.
The wavespeed is the speed at which a wavefront travels through the medium. The wavespeed of a wave through a particular medium is a constant.
Wave properties include: reflection at a boundary; refraction due to a change of speed; diffraction through gaps and around corners; interference producing areas of higher and lower intensity
The wave equation v = f λ relates wavespeed, v, frequency f, and wavelength, λ.
Electromagnetic Waves
Electromagnetic waves are oscillations in the field strength of the electric and magnetic fields at a point.
Electromagnetic waves are produced by accelerated charges.
Electromagnetic waves travel through a vacuum at the speed of light, c = 3×108m/s.
The electromagnetic spectrum is arranged in order of increasing energy and frequency into radio waves, microwaves, infrared, visible light, ultraviolet, X-rays and gamma rays.
Radio waves have metre and kilometre wavelengths. Microwaves have cm wavelengths. Infra red radiation is emitted by warm objects and has μm wavelengths. Visible light has wavelengths of 300-700nm. Ultra violet has nm wavelengths. X rays have nm and pm wavelengths. Gamma rays are produced during radioactive decay and have pm wavelengths.
Imaging
EM waves are used in imaging because of the different absorptive properties of materials or the different reflective properties of surfaces.
A medical X-ray image is produced due to the differential absorption of X-rays by tissues in the human body, and the effect of the transmitted X-rays on photographic film.
Backscatter X-ray images are produced by the reflection of X-rays from an object.
RADAR (radio detection and ranging) relies on measuring the time of flight for a radio wave to be reflected from an object.
‘Stealth’ technologies rely on surfaces which are highly absorbent of EM radiation, and are smooth enough to reflect radiation in one particular direction rather than scattering it back to a detector.
Infra red cameras image the heat radiation emitted by an object warmer than its surroundings.
Reflection
Black surfaces absorb light radiation and white or shiny surfaces reflect it.
For waves reflected at a plane surface, angle of incidence = angle of reflection.
Waves reflected from a rough surface are scattered.
A virtual image is formed in a plane mirror at the same distance behind the mirror as the object is in front of the mirror.
Refraction
When a wave passes a boundary between two mediums, it changes speed.
A refracted ray changes direction unless it passes the boundary along the normal.
A ray passing from a more dense to a less dense medium is refracted away from the normal and from a less to a more dense medium, refracted towards the normal.
The relative refractive index of the medium is given by the ratio of the speed of electromagnetic waves in a vacuum to the speed in the medium. n = v1/v2
The angle of incidence, θ1, is related to the angle of refraction, θ2, through the formula sinθ2/sinr θ1 = v2/v1
Total internal reflection occurs where the angle of refraction is greater than the critical angle.
Lenses
Convex lenses can form both real and virtual images.
The focal length measures how strongly the light rays passing through a lens converge.
Standard rays can be used to find the position of an image in a ray diagram.
The linear magnification of a lens is the ratio of image size to object size.
Wave-particle duality
Electromagnetic waves can also be considered as particles- photons- where the energy of the photon is given by E = hf where h is Planck’s constant and f is the frequency of the radiation.
Light can show both particle and wave properties in two slit diffraction experiments.
Planetary systems
Assessment: crit BE Solar system Data Processing task, Exoplanets Data Processing task crit DECraters Investigation
Forces
If one object exerts a force on another, there is a force of equal magnitude in the opposite direction exerted by the second object on the first. (Newton’s third law)
The resultant force is the vector sum of the forces acting on the object, where the components of the force are given by Fcosθ and F sinθ.
The horizontal component of an object’s velocity does not affect its acceleration towards the Earth, unless the velocity is large enough that the curvature of the Earth is significant.
Pressure
Pressure is the force exerted per unit area, and is calculated by Pressure = Force/Area
Units of pressure include N/m2, Pa and mmHg.
Newton’s law of gravitation
Every object in the universe attracts every other object and larger masses attract more, but the force between them decreases as the distance gets larger.
The gravitational force can be calculated from F = Gm1m2/r2 where G is the universal gravitational constant 6.67 × 10-11 m3kg-1s-2.
Circular motion and orbits
The gravitational force causes planets to orbit around stars and satellites to orbit around planets.
The time period of an orbit is the time for one complete rotation.
A centripetal force is needed to keep an object orbiting in a circle. If the centripetal force is removed, the object will travel at a tangent to the circle at constant velocity. (Newton’s 1st law of motion)
A greater centripetal force is needed when the object is moving with a higher velocity, or is orbiting in a circle with a smaller radius.
The centripetal force, F = mv2/r where m is the mass, v is the velocity, and r is the radius of the orbit.
The Solar System
The Solar System is composed of the Sun, the 8 major planets, comets, and asteroids (planetoids)
Mercury, Venus, Earth and Mars are rocky planets. Jupiter, Saturn, Uranus and Neptune are gas giants.
Earth, Mars and the four gas giants have moons which orbit around them.
In general, the further the planet is from the Sun, the lower the surface temperature.
The rocky planets have a variety of atmospheres. The atmosphere of Venus is high in carbon dioxide and sulphur dioxide and this accounts for the anomalously high surface temperature of Venus.
Kepler’s laws
Kepler’s laws of planetary motion describe the orbits of planets around a star.
Planets orbit in ellipses around the star.
The line joining a planet and the sun sweeps out equal areas in equal times.
The square of the orbital period is proportional to the cube of the orbital radius for a circular orbit.
Detecting exoplanets
Exoplanets are planets which have been discovered orbiting stars other than the Sun.
Exoplanets are usually found around nearby stars.
Most of the currently known exoplanets are thought to be gas giants as these are easier to detect.
Exoplanets are detected by the radial velocity method, by detecting transits or by gravitational microlensing effects.
Using Excel spreadsheets for graphing and calculations
Spreadsheets can be used to perform repeated calculations on data.
A variety of graph types can be produced using a spreadsheet.
CERN and particle physics
Assessment: crit AB CERN essay
Radioactivity
An atom consists of protons and neutrons in the nucleus and electrons arranged in shells.
The atomic number of an atom is the number of protons in the nucleus.
The mass number of an atom is the number of neutrons and protons in the nucleus.
One atomic mass unit (amu) is approximately the mass of a neutron or proton.
Isotopes of an element are atoms with the same number of protons but different numbers of neutrons.
The protons and neutrons in the nucleus are held together by the strong nuclear force.
Unstable isotopes can undergo radioactive decay, emitting energy and matter.
An alpha particle consists of 2 neutrons and 2 protons, and has a +2 charge and a mass of 4amu.
A beta particle consists of a fast moving electron and has a charge of -1.
Gamma rays may be emitted during radioactive decay.
Alpha, beta and gamma radiation are ionizing radiation- they create ions as they pass through matter.
The activity of a sample of radioactive material is measured in Becquerels where 1 Bq = 1 decay/s
The half life of an isotope is the time for the activity of a sample of a radioactive isotope to fall by ½.
Particles in magnetic and electric fields
Charged particles are accelerated in electric (E) fields where the force on the particle, F = qE where q is the charge in Coulombs and E is the electric field strength in Volts. The force is in the direction of the field.
Moving charged particles are accelerated in magnetic (B) fields where the force on the particle,
F = qvB where q is the charge in Coulombs, v is the velocity of the particle and B is the magnetic field strength in Teslas. The force is perpendicular to velocity.
Particles moving in magnetic fields move in circles.
Momentum is conserved during an interaction, so the total momentum before a collision is the same as the total momentum afterwards.
Particle accelerators
A particle accelerator uses electric fields to accelerate a particle to high speeds (high energies).
A linear accelerator speeds up particles in straight lines using electric fields.
A circular particle accelerator uses magnetic fields to accelerate particles in circles and electric fields to speed up the particles.
Particles in particle accelerators are forced to collide, and these collisions at high energies produce particle debris.
Momentum
Momentum is a vector quantity given by p = mv
Impulses change the momentum of an object. An impulse is the force × the time it acts for. I = Ft
Newton’s second law can also be written in terms of momentum as Ft = ∆p
Energy
Energy and matter can be interchanged with the amount of energy calculated from E=mc2 where c is the speed of light in a vacuum c = 3×108
When particles are created from energy, a particle and an antiparticle are created together. When a particle and antiparticle meet, they annihilate, producing energy as a photon.
The electron volt is an alternative unit of energy where 1eV = 1.6×10-19J
Leptons and Hadrons
Leptons are point particles that don’t feel the strong force and include the electron, muon, tau, and neutrinos.
Hadrons feel the strong force and include quarks, protons and neutrons and atomic nuclei
Protons and neutrons are each made of 3 quarks held together by the strong force.
Fundamental forces
The four fundamental forces are gravitational, electromagnetic, strong nuclear and weak nuclear force.
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