Demonstrate the coefficient of static friction between a level wooden ramp and a weighted wooden sled.
A bucket into which water is added is used to create a force of tension in a string attached to a weighted wooden sled. The volume of water is an indirect measurement of the mass of the bucket.
Mass of the wooden sled without weights is 144 grams
Mass of the bucket without water is 225 grams
Calculations were done using just the Mass as "g" cancels when dividing the forces.
| Mass of weighted sled | Volume of water placed into bucket | Force of friction Total mass of bucket |
Coefficient of static friction
Mu = Force / Normal force |
| 1.144 Kg | .276 L | .475 Kg | .415 |
| .25 L | .475 Kg | .415 | |
| .30 L | .525 Kg | .459 | |
| 2.144 Kg | .875 L | 1.1 Kg | .513 |
| .875 L | 1.1 Kg | .513 | |
| .875 L | 1.1 Kg | .513 | |
| 3.144 Kg | 1.6 L | 1.825 Kg | .580 |
| 1.4 L | 1.625 Kg | .517 |
Demonstrate that it is possible to determine coefficient of static friction by using a ramp and measuring the angle required to make sled move.
Class placed a wooden sled on a board and lifted one end of the board slowly until the sled begun to move on the ramp. The angle of the board was then measured and the coefficient of static friction was calculated as the arc tan of the angle. The derivation of this relationship was shown on the board following the collection of data.
| Mass of sled | Angle of ramp | Mu static |
| 1.1445 Kg | 24 d | |
| 26 d | ||
| 24 d | 0.459 | |
| 2.144 Kg | 27 d | |
| 22 d | ||
| 20 d | 0.424 | |
| 3.144 Kg | 23 d | |
| 23 d | ||
| 23 d | 0.478 |
One explanation of the lower values in this experiment is the cleaning of the board ramp and the bottom of the sled with a paper towel before these runs. There were some rough edges on the sled and it was clear that some dirt was removed.