Pendulum Notes

Period (T) Time for Swing (back and forth…return to start) T=2π where l= length of string (m) and g = gravity (9.8 m/s 2 on Earth) Units are seconds

Frequency (F) # of oscillations in 1 sec F = units of sec -1 or Hertz (Hz)

Amplitude max distance from equilibrium You can measure angle (  ) as shown in picture. For our lab, we measured starting height of the bob

Test your knowledge What forces are acting on the pendulum? Force of Gravity (Fg) and Tension force (Ft) which is the force up the string (rod) In the picture above is the bob speeding up? Slowing down? No change? Slowing down (will be at a complete stop just before turn around)

Lab Results What did you discover about the effect of the following on swing time? Mass? – No effect String Height? – No effect String Length? – Increase in length = increase in oscillation time

Total Energy in the System Total Energy (Mechanical Energy) = KE + PE During the swing, there is a constant exchange between KE and PE. At max height, max PE (PE = W*H) At bottom of pendulum, H is lowest, so PE is at lowest point (PE =0) and KE is at the highest At the bottom of pendulum, the speed is the greatest. (KE = ½ mV 2 )

Pendulum Math