physics hard questions

• Planets


  • Orbit the sun in a slightly elliptical orbit (stretched circles)
  • Orbit on the same plane
  • Travel in the same direction
  • Orbit at different distances, speeds and times
  • Sun is at the centre of the planet's orbit
• Moons


  • Orbit planets in circular paths
  • The closer the moon is to the planet the shorter time it will take to orbit and the greater the speed of the orbit
• Comets


  • Have highly elliptical orbits (stretched) or hyperbolic orbits
  • As the comet approaches the sun, its speed increases rapidly
  • When it is further, it has a lower speed
• Longitudinal waves


  Oscillate parallel to the direction of the wave
• Transverse waves


  Oscillate perpendicular to the direction of the wave
• Light waves are transverse waves
• Sound waves are longitudinal
• Light waves are electromagnetic, sound is not
• Light can travel through a vacuum while sound cannot
• Planets have different masses and so they have different gravitational field strengths at their surfaces
• Alpha radiation can cause cell mutation but it is only dangerous when in the body, and it is blocked by skin
• Current


  The rate of flow of charge
• Orbital speed


  (2 x pi x orbital radius) / time period
• Background radiation


  Measured by subtracting the background count rate from the count rate of the radioactive isotope
• Electromagnetic waves are all transverse waves
• Light waves are transverse waves, sound waves are longitudinal waves
• Force


  Mass x acceleration
• Distance


  Area under a speed-time graph
• Reduction in temperature


  Reduces the kinetic energy of the particles
• Fewer collisions with the walls of the container per unit time

  Each collision is less hard and the force per unit area decreases
• When a current passes through a coil

  1. Magnetic field is formed

  2. Field interacts with the field being produced by the magnet

  3. Force is exerted on the coil

  4. Coil begins to oscillate and rotate
• Terminal velocity


  When an object is falling, the weight is more than the drag, but the resultant forces causes acceleration and so drag begins to increase with speed. When air resistance and weight equal to each other, the object falls at a constant speed
• Current might not be proportional to voltage in a filament lamp


  Current heats up filament and the resistance changes with temperature
• Nuclear fission


  The splitting of two large nuclei to form two radioactive daughter nuclei
• Nuclear fusion

  Two light nuclei collide at a high speed to fuse and create one heavier nucleus
• Fusion reaction

  • Reactants are not as hazardous as compared to a fission reactor
  • Products of fusion are not radioactive so there are no mutations or damage to cells
  • No shielding required
  • No long-term storage problems
• Plastic

  Poor conductor of heat
• Metal

  Good conductor of heat
• Power

  Unit is Watts (W)
• Improving reliability of data

  1. Repeat the experiment

  2. Find the mean

  3. Remove anomalies from the data
• Doppler effect

  When the object retreats, the frequency will decrease and the wavefronts will stretch. This increases the wavelengths and the speed of the waves is constant but the sound becomes quieter
• Compass needles turn when the current is switched on

  Current provides a magnetic field and magnets experience a force
• When the current in the wire is reversed

  The magnetic field changes direction
• Producing a current in the wire

  1. Wire is moved in the magnetic field

  2. Cutting field lines induces a voltage across the wire

  3. Voltage gives a current as there is a complete circuit