User:OldakQuill/Revision/Physics

From Wikipedia, the free encyclopedia
Jump to: navigation, search

1[edit]

1 - Scalars and Vectors[edit]

  • distinguish between scalar and vector quantities and give examples.
Scalars have magnitude (size) only - electric charge, distance, mass, speed, temperature, time, and energy
Vectors are quantities with magnitude AND direction- displacement, velocity, electric field, momentum, force, and acceleration.
  • use a vector triangle to determine the resultant of two coplanar vectors - see trigonometry
  • calculate the resultant of two perpendicular vectors - Pythagoras' theorem
  • resolve a vector into two perpendicular components - verticle and horizontal - again using trigonometry.
  • understand the independent nature of perpendicular components of a vector - a perfectly horizontal force has no verticle component.

2 - Kinematics[edit]

  • define the following:
  • use graphical methods to represent distance travelled, displacement, speed, velocity and acceleration.
  • find the distance travelled by calculating the area under a speed-time graph.
  • use the slope of a displacement-time graph to find velocity, and of a distance-time graph to find speed.
  • use the slope of a velocity-time graph to find acceleration.
  • derive, from the definitions of velocity and of acceleration, equations which represent uniformly accelerated motion in a straight line:
    • v=u+at
    • v2=u2+2as
    • s=[half](u+v)t
    • s=ut+[half]at2
  • use equations which represent uniformly accelerated motion in a straight line, including falling in a uniform gravitational field without air resistance.
  • interpret displacement-time and speed-time graphs for motion with non-uniform acceleration.
  • explain motion due to a uniform velocity in one direction and a uniform acceleration in a perpendicular direction - a bullet is fired and a bullet is dropped - they will take the same time to reach the ground due to gravity. The acceleration only acts on the bullet in a horizontal direction - gravity only operates on a verticle plane.

3 - Dynamics[edit]

  • demonstrate an understanding that mass is the property of a body which resists change in motion.
  • define and use the equation density = mass/volume.
  • recall and use the equation F = ma, in situations where mass is constant, appreciating that force and acceleration are always in the same direction.
  • define the newton - amount of force required to accelerate a mass of one kilogram at a rate of one metre per second squared.
  • describe and use the concept of weight as the effect of a gravitational field on a mass.
  • recall and use the relationship weight = mass x gravitational field strength.
  • describe qualitatively the motion of bodies falling in a uniform gravitational field with fluid resistance. The body accelerates as weight far outbalances resistance; as the fall continues the air resistance increases with velocity - the acceleration of the falling body decreases. Eventually the air resistance and weight are equal - there is no more acceleration - it is at terminal velocity.

4 - Force, Work and Power[edit]

  • understand that the weight of a body may be taken as acting at a single point known as its centre of gravity.
  • understand a couple as a pair of equal parallel forces tending to produce rotation only.
  • define and use the moment of a force (moment = force x perpendicular distance from pivot) and the torque of a couple (N m).
  • show an understanding that, when there is no resultant force and no resultant torque, a system is in equilibrium - resistance to change.
  • apply the principle of moments to solve problems involving forces acting in two dimensions.
  • define pressure: is the force per unit area
  • recall and use the equation p = F/A
  • understand the concept of work in terms of the product of force and displacement in the direction of the force.
  • define the joule: work required to exert a force of one newton for a distance of one metre (so Newton Metre, Coulomb Volt or Watt second)
  • recall and use the equation W = Fx, where F is a constant force along the direction of motion.
  • recall and use equations for kinetic energy ∆Ek = ½ mv2 and change in gravitational potential energy ∆Ep = mg∆h.
  • relate power to work done and time taken. (P = W/t)
  • define the watt: the rate in joules per second at which energy is being converted, used, or dissipated
  • recall and use the equation W = Pt.

5 - Deformation of Solids[edit]

6 - Forces on Vehicles[edit]

  • understand the terms motive force (a force which drives the vehicle) and braking force (force which stops the vehicle).
  • describe how driving wheels can generate a motive force (friction against road, force against road is greater than cars weight, due to friction when turn - car move).
  • explain the importance of friction in acceleration and deceleration - allows acceleration and deceleration to occur, bodies like to stay as they are - not speeding up or slowing down).
  • recall and use the relationship motive power = driving force x speed.

Car safety[edit]

3[edit]

1 - Dynamics[edit]

  • state each of Newton’s laws of motion: First - A body's center of mass remains at rest, or moves in a straight line (at a constant velocity, v), unless acted upon by a net outside force. | Second - The acceleration of an object of constant mass is proportional to the resultant force acting upon it. | Third - Whenever one body exerts force upon a second body, the second body exerts an equal and opposite force upon the first body. (Momentum is conserved)
  • define, recall and use (linear) momentum as the product of mass and velocity. (p=mv)
  • define force as rate of change of momentum (F=p/t), and use this definition in situations where mass is constant.
  • state the principle of conservation of momentum for an isolated system in any direction the total momentum before an interaction is equal to the total momentum after interaction
  • use the principle of conservation of momentum in simple applications including elastic interactions (where kinetic energy is maintained) and inelastic interactions between two bodies in one dimension, and the separation of an initially stationary object into two parts. (Knowledge of the concept of coefficient of restitution is not required.)

2 - Work and Energy[edit]

  • give examples of energy in different forms, its conversion and conservation, and apply the principle of energy conservation to simple examples.
  • calculate the work done by a constant force in situations including those where the force is not in the same direction as the displacement - so work done by tension = Td; against friction = -Fd; by gravity = -mgxh (work out weight acting down slope by mg sin [theta])
  • recall and use the equation for kinetic energy, Ek = ½mv2 .
  • recall and use, the equation ∆Ep = mg∆h for potential energy changes near the Earth’s surface.

3 - Motion in a circle[edit]

  • describe qualitatively motion in a curved path due to a perpendicular force (an unbalanced force which acts at right-angles to the velocity, towards the centre of the circle), and understand the centripetal acceleration in the case of uniform motion in a circle (as the velocity is always changing in a circle, it is accelerating).
  • express angular displacement in radians - a complete circle is 2[pi]radians.
  • recall and use centripetal acceleration a = v2 / r.
  • apply the equation F = ma to uniform motion in a circle to derive F = mv2 / r.

4 - Oscillations[edit]

  • understand and use the terms displacement (distance from point of rest), amplitude (magnitude of displacement), period (oscillations per time), frequency (time per oscillation) and phase difference (how much, per cycle, two waves are out of sync).
  • express period in terms of frequency (P=1/f).
  • define simple harmonic motion - acceleration is proportional to a bodies displacement from a fixed point, and is directed towards that point.
  • describe graphically the changes in displacement, velocity and acceleration during oscillations.
  • understand velocity as the gradient of the displacement-time graph.
  • recall and use a = -(2π f)2x, and the solutions x = Αsin2πf t, x = Αcos2πf t for simple harmonic motion.
  • describe practical examples of damped oscillations with particular reference to the effects of the degree of damping in such cases as a car suspension system (critical damping - if it were heavy suspension would not work), swing slowing due to friction between frame and swing and swing and air.
  • describe practical examples of forced oscillations and resonance - Tacoma Narrows bridge disaster, pushing child on swing at same frequency as natural frequency is resonance (amplitude increases)
  • describe graphically how the amplitude of a forced oscillation changes with frequency near to the natural frequency of the system - peak at natural frequency with less gradient on left.

5 - Gravitational Fields[edit]

6 - Electrical Fields[edit]

  • understand an electric field as an example of a field of force and define, recall and use electric field strength as force per unit positive charge.
  • use field lines to represent an electric field (lines from positive to negative).
  • recall and use Coulomb’s law for point charges in a vacuum in the form F = kQ1Q2 / r2, where k = 1 / 4π ε0.
  • recall and use E = kQ / r2 for the electric field strength of a point charge.
  • recall and use E = V/d for the magnitude of the uniform electric field strength between charged parallel plates.
  • recognise the similarities of, and differences between, electric fields and gravitational fields - differ in what they are force over; differ in units (both define force as Newton); both have parallel field lines; force given by different laws (Newton and Coulomb), field strength therefore given by other shorter equations

7 - Capacitors[edit]

  • define capacitance (Charged stored per unit potential difference across it) and the farad (coulomb per volt).
  • recall and use C = Q / V.
  • use formulae for the capacitance of capacitors in series (1/C1 + 1/C2...) and in parallel (C1 + C2...).
  • recall and use W = ½QV, for the energy of a charged capacitor.
  • describe the discharge of a capacitor through a resistor (gradually discharges, QIV all decrease), sketch graphs showing the variation with time of the potential difference, charge stored and current during this discharge (all exponential decay, voltage initially large due to great PD over capacitor - QI also decrease as related to V by Q=CV and V=IR - if capacitor is charged up by 10V cell, the initial voltage will be 10V. The gradient of charge-time is current; area under current-time is charge).
  • appreciate the practical importance of time constant for discharge of a capacitor through a resistor - it equals CR, it is the time taken for the current, charge or pd to fall to 1/e of inital value - twice time constant is 1/e2. So greater C or R longer time constant.
  • recall τ = CR for the time constant of a capacitor-resistor circuit.
  • use equations of the form x = x0 e-t/CR for the discharge of a capacitor.

8 - Electromagnetism[edit]

  • recall and use F = BIlsin θ , with directions as interpreted by Fleming’s left-hand rule, for the force on a current-carrying conductor in a uniform magnetic field.
  • recall and use F = BQv , for the force on a charge moving in a uniform magnetic field.
  • analyse the circular orbits of charged particles moving in a plane perpendicular to a uniform magnetic field by relating the electromagnetic force to the centripetal acceleration it causes. (because F is perpendicular to v - Bev = mv2/r [therfore] r = mv/Be. The greater the velocity/mass, the greater the orbit - a stronger field causes tighter circles)

9 - Electromagnetic induction[edit]

  • define magnetic flux (measure of quantity of magnetism, taking account of the strength and the extent of a magnetic field) and the weber (Volt-second).
  • recall and use Φ = BA.
  • define magnetic flux linkage, N Φ.
  • recall and use Faraday’s law of electromagnetic induction - E = dΦ/dt
  • recall and use Lenz’s law to determine the direction of an induced e.m.f - any induced current will flow in a direction as to produce effects which oppose the change that is producing it.
  • recall and use the equation magnitude of induced e.m.f. = rate of change of flux linkage.

10 - Thermal Physics[edit]

  • show an awareness that internal energy is determined by the state of the system and can be expressed as the sum of a random distribution of kinetic and potential energies associated with the molecules of the system.
  • relate a rise in temperature of a body to an increase in internal energy.
  • demonstrate knowledge that there is an absolute scale of temperature which does not depend upon the physical property of any particular substance, i.e. the thermodynamic scale.
  • appreciate that, on the thermodynamic (Kelvin) scale, absolute zero is the temperature at which all substances have a minimum internal energy.
  • show familiarity with temperatures measured in kelvin and degrees Celsius - +273.
  • define and use specific heat capacity, and show an awareness of the principle of its determination by an electrical method - the energy required for a specific material to rise by a temperature.
  • recall and use ∆Q = mc∆ θ.
  • describe melting and boiling in terms of energy input without a change in temperature - greater disorder leading to greater potential energy (where simple temperature rise is increase in kinetic energy).
  • recall and use the ideal gas equation pV = nRT, where n is the amount of gas in moles.
  • appreciate that one mole is 6.02 x 1023 particles and that 6.02 x 1023 mole-1 is the Avogadro constant NA .
  • recall that the mean kinetic energy of a molecule of an ideal gas is proportional to the thermodynamic temperature.

11 - The Nuclear Atom[edit]

  • demonstrate a qualitative understanding of the α-particle scattering experiment and the evidence this provides for the existence, charge and small size of the nucleus - alpha-particles bombarded on gold foil. Most passed through, some were deflected (showing concentrated area of opposite charge)
  • demonstrate a qualitative understanding of X-ray diffraction and the evidence this provides for crystal structure - X-rays directed at crystal, spacing between atoms similar to wavelength of X-ray, so X-ray diffracted.
  • demonstrate a qualitative understanding of neutron diffraction and the evidence this provides for crystal structure. - not charged, magnetic - so interact with atoms of magnetic elements, provides information on pattern in which nuclei in solid material distributed.
  • demonstrate a qualitative understanding of electron diffraction and the evidence this provides for the spacing of atoms - beam of electrons diffracted by planes of atoms in crystal - similar to X-ray.
  • demonstrate a qualitative understanding of high-energy electron scattering and the evidence this provides for the radius of the nucleus - as nucleus is smaller, smaller wavelength is needed. (de Broglie equation). So only diffracted as pass around nuclus, showing diametre.
  • show an awareness of the relative sizes of nuclei (10-15 to 10-14 m), atoms (10-10 m) and molecules (10-10 to 10-6 m).
  • distinguish between nucleon (mass) number and proton (atomic) number.
  • understand that an element can exist in various isotopic forms, each with a different number of neutrons.
  • use the usual notation for the representation of nuclides and represent simple nuclear reactions by nuclear equations.
  • appreciate the equivalence between mass and energy, and recall and use the equation ∆E = ∆mc2.
  • appreciate that nuclear processes involve the conservation of charge and of massenergy.
  • describe the processes of nuclear fission (splitting of unstable nucleus into two or more more stable nucleus) and nuclear fusion (light nuclei join to form more massive one) and appreciate that these reactions involve a release of energy.

12 - Radioactivity[edit]

  • appreciate the spontaneous and random nature of radioactive decay of unstable nuclei.
  • describe the nature, penetration and range of α-particles (Helium, paper, cms), β-particles (electron, aluminium, metres) and γ-rays (electromagnetic wave, kilometres, cms lead) as different types of ionising radiation.
  • represent radioactive decay by nuclear equations.
  • show an awareness of the hazards of ionising radiation (kill tissue, damage DNA, break up water) and the safety precautions which should be taken in the handling (distance), storage (containers which overcome penetrating force) and disposal (protection of environment) of radioactive materials.
  • define the terms nuclear activity (rate at which nuclei decay - decays per second Bq) and decay constant (likelyhood that an individual nucleus will decay per unit time).
  • recall and use A = λN.
  • recognise, use and represent graphically solutions of the decay law bases on x = x0e- λt for activity, number of undecayed nuclei and corrected count rate - all have half life, some decay faster than others.
  • define half-life as the mean time for the number of nuclei of a nuclide to halve.
  • use the relation λt½ = 0.693.