Do drop a line to Terry Dactyl for friendly hints/tips in answering these questions. If you send in some correct answers he might even send you a list of his favourite Stone-Age web sites!

• 1. Calculate the rate of rotation, in revolutions per minute, of a space station which is 120 m. in diameter, if normal gravity (g = 9.8m/s) is maintained at the edge.
• 2. A solid cylinder of radius 5 cm and height 20 cm rests on its circular end 20 cm from the center of a rotating disk. Calculate the rate of rotation of the disk, in revolutions per minute, at the point where the cylinder falls over.
• 3. A rock group performing at Wembley Stadium is being broadcast. Explain with the aid of approximate calculations how the audience listening at home hear the sound momentarily before the live audience in the back row.
• 4. A pair of ions in a crystal of Lithium Fluoride attract each other with a force depending on their separation. Sketch a graph showing the energy (y-axis) of such a pair as a function of their separation (x-axis). Be careful about the minimum and maximum separations. Mark the equilibrium point and explain its position. Explain what might happen when the ions, motionless at their equilibrium point, have some energy input.
• 5. The sparking plug is a device in petrol-engined cars for igniting the fuel-air mixture. A voltage sufficient to cause ionisation of the vapour must be applied by an induction coil, whose primary winding is switched rapidly. (a) If the mixture ionises at 2.4 million volts per metre and the plug gap is 1.1 mm, what voltage must the coil generate? (b) Estimate the turns ratio of the induction coil when a 12 volt car battery is used.
• 6. Prove that the acceleration of a body moving at a constant speed v in a circle radius r is v²/r. Show that this is dimensionally correct.
• 7. A pair of cylindrical electromagnets is placed end-to-end, with opposite poles closest to produce a strong magnetic field in the cavity. The apparatus is evacuated, then a beam of particles is fired into the cavity. Draw a sketch of the apparatus, and show approximate trajectories when (i) electrons , (ii) protons and (iii) neutrons are used as the particle beam.
• 8. Sketch length vs. tension graphs for the following materials, explaining interesting points:
  (i) rubber
  (ii) blu-tack
  (iii) gold
  (iv) brick
  (v) a steel spring and a steel wire on the same graph
• 9. An inductance of 2.5 H. and negligible resistance is connected in series with a 10 ohm resistor and a 5V. DC supply. The circuit is completed at time t=0. Sketch a graph of the current as a function of time, showing the scale on each axis carefully. You will need to calculate the rate of rise of current at t=0.
• more coming soon!