sledding+<3

Sup ladies and gents this is our sledding lab = Dashing through the Snow =


 * __Primary Authors:__** Sara Meinecke, Carly Goranson, Maureen Maginot

__**Abstract:**__
 * Goal:** To find the effect of velocity on the coefficent of friction.

__**Introduction:**__ We know that velocity should not affect the coefficient of friction and we would like to confirm this theory.

__**Methods:**__

The effect of velocity on the coefficient of friction: We attached a sled to the back of a pick-up truck, along with a manual force probe (as seen in picture below). In addition, we placed a brick in the sled to make the force readable. In total, the mass of the sled and brick is 3.175 kg.

We completed three trials for three different velocities: 10, 15, and 20 miles per hour or 4.47, 6.7, and 8.94 m/s. We did not record the force until the speed was constant, thus the acceleration is zero. We measured the height from the truck to the ground, and also the distance from the car to the sled and used the inverse of tangent to find theta.

__**Data:**__

As you can see, our data is strikingly similar, so we took the average tension force for each speed and applied it to our equations to find the force of f9riction and eventually, the coefficient of friction. The average force of tension when velocity is 10 mph is 7.33 N (figure 1 below) and the average force of tension for both 15 mph and 20 mph is 7.67 N (figure 2 below).
 * || Trial 1 || Trial 2 || Trial 3 ||
 * v=4.47 m/s || 7 N || 8 N || 7 N ||
 * v=6.7 m/s || 8 N || 7 N || 8 N ||
 * v=8.94 m/s || 8 N || 7 N || 8 N ||

Because acceleration is 0, the horizontal force of tension is equal to the force of friction. Using the diagrams above, we found the following data: When v=4.74 m/s, the horizontal force of tension is 5.76 N, therefore the force of friction is 5.76 N as well. When v=6.7 and 8.94 m/s, the horizontal force of tension is 6.02 N, therefore the force of friction is 6.02 N as well.

We then found the force of gravity, universal for all speeds, to be 31.12 N. We subtracted the vertical force of tension from the force of gravity to find the normal force, because no vertical velocity exists. Therefore the normal force and the vertical force of tension are equal to the force of gravity. To find the coefficient of friction for each speed, we divided the frictional force by the normal force, and found:

__**Results:**__ When v=4.74 m/s, the coefficient of friction is 0.216. When v=6.7 and 8.94 m/s, the coefficient of friction 0.228.

There is a difference of 0.012 between the two results. This can most likely be explained by human error, whether it was the manual force probe we used or slightly skewed measurements.

__**Conclusion:**__ This experiment has confirmed that indeed, velocity does not affect the coefficient of friction. Although we did experience a bit of human error, our results turned out to be very similar, with a percent difference of almost zero. Over all we feel that our results were successful.