The Biomechanics of Skating: Linear Kinematics

Getting Started

In these activities, you will be doing calculations. So, before you start, have these materials handy: pencil, paper, calculator and a table provided for you (just click on table and print a hardcopy). We will be working in the metric system. If necessary, review the units: meters, seconds, kilograms, newtons, etc.

Print the Worksheet

Before we begin our lesson in linear kinematics, lets look at a quick activity in position and scale factors.

The position of the luge at any moment is simply its location on the track, measured from a known reference point. For example, a convenient reference point might be the starting line, which is a few meters down the track from the point where the sled is released. So, at the start, we could then say that the sled's position is 0 meters, and at the end of a particular segment, its position is equal to the length of that segment. So giving the sled's position, in meters lets us know exactly where the sled is located.

Here is a simulated luge starting sequence. Use the starting line as the reference point on the track from which to measure the luge position. There is a dot on the slider that you can use as a reference point from the starting line.

Now, using a plastic ruler, measure the distance on the screen from the reference point on the track to the dot on the luge. For each image, this distance specifies the position of the luge. Record your answers in the table under Screen Position.

There is one problem that we've avoided so far -- what we see on the screen is reduced in size compared to the true size of the luge track. In order to specify the luge position correctly, we have to find the relationship between distances measured on the screen and those measured on the track. That is, we must find the correct scale of the image. The easiest way to do this is to find an object whose true size is known, and measure its length in the image. Then multiplying any length, as measured on the screen, by the scale factor gives the true length.

Use the legend measurement provided to help find the scale factor for your true position measurements. Compute the true position of the luge for each image in the sequence. Record each number in the table under True Position.