Newton’s Second Law

Free Body Diagram

In the example above, the two forces on the slider were acting along the same line, which made it easy to do the vector addition. With a moving luge we may have to account for forces acting in several different directions.

One really good way to “see” the forces acting on an object is to draw a free body diagram. This is a rough drawing of the object with an arrow for each force that acts on it. The size and direction of the arrow indicates the size and direction of the force. The picture of the slider on the scale is an example of such a diagram.

To draw a free body diagram:

  1. Draw a simple representation of the object in question. For clarity, show only the object -- not anything else that might actually be in contact with it.
  2. Consider all the forces acting on the object, and note the direction in which each one is acting.
  3. Draw each force as an arrow, with the tail of the arrow on the object and the head pointing in the proper direction.

In the men’s doubles, the heavier partner is placed on top of and forward from the bottom, lighter slider. Why?

In our earlier activity we actually found the acceleration by analyzing images of the luge's motion. Let's work backwards to see what we can conclude about the forces acting on the luge.

Draw a free body diagram of the luge on the track in the situation just shown.
Winter Olympics Course Outline Comments Questions

© April, 1998, Montana State University-Bozeman