practical 3 - determination of g

• equipment

  • stand and clamp
  • electromagnet
  • steel ball bearing
  • light gate
  • stopwatch
• method

  • set up apparatus
  • adjust position of lower light gate so height is 0.5m
  • turn on electromagnet and attach ball bearing
  • zero stopwatch and switch off electromagnet
  • record time on the stopwatch
  • reduce height by 0.05m by moving lower light gate upwards
  • repeat reducing height by 0.05m each time down to 0.25m
  • repeat experiment twice more and find the mean
• graphs and calculations

  • plot graph of 2h/t against t and draw line of best fit
  • gradient is g
  • $h=$$ut+$$\frac{1}{2}gt^2\ \rightarrow\ \frac{2h}{t}=$$2u+$$gt$
  • y intercept is 2u (u is speed of ball bearing when at top light gate)
• safety

  • toppling over and causing injury

  precaution

  • use counterweight or clamp the stand to the table
• improvements

  • distance between upper light gate and starting position of the ball bearing must be kept constant
  • reaches upper light gate with same speed each time
  • ball bearing can be cushioned by a pad inside tray at bottom of clamp so it doesn't fall of dangerously
  • dense ball bearing to mitigate effects of air resistance
  • clamp ruler directly next to light gates to reduce parallax error in measuring height