1J10.20 Metre Stick on Fingers
Centre-of-gravity, dependence of friction on the normal force, balance of torques
A meter stick is supported on the two forefingers. The fingers are moved slowly together and end up at the center of gravity of the stick.
-  Meter stick
-  200 gram weight
-  plexiglas cylinder and a cork covered piece of wood
- Optional: an 8 foot length of 2" x 2" and a 1 kg weight
- Place the meter stick on your forefingers with one finger at 0cm and one at 100cm.
- Slowly move your fingers together. Your fingers will alternate between slipping and sliding along the stick and will come together at 50cm, the center of gravity.
- Place a 200 gram weight on one end of the meter stick.
- Repeat steps 1 and 2. The center of gravity has moved because of the weight and your fingers will come together on the side with the weight.
- Repeat steps 1 through 4 using a plexiglass cylinder and a cork covered piece of wood instead of your fingers to show this works when the coefficients of friction of the supports are different.
- (Optional) Repeat steps 1 through 4 above using an 8 foot length of 2" x 2" in place of the meter stick. Using a 1kg weight on the end moves the center of gravity to 70cm from the end.
- PIRA 1J10.20
- Video Encyclopedia 04-15
- Sutton M-50; DaR M-478; Taylor 1.23 p47; Ehrlich(1) D9 p49; Miller p16; Kutliroff 47 p106; Freier Fig 10.8 p100; Steinhaus p140
- Don't attempt this at home!
- Assembled from lab equipment
If you have any questions about the demos or notes you would like to add to this page, contact Ricky Chu at ricky_chu AT sfu DOT ca.