Right Hand 90-Degree Quadrant Method of Linear Momentum  E-mail this product to a friend

Right Handed 90-Degree Quadrant Method of Linear Momentum
by Wiley L. Howell

Not everybody has gone over to the left-hand 360-degree way of doing linear momentum. Physicist and engineers - particularly those who do not regularly work in traffic crash reconstruction - may not even be familiar with this newer, easier, counterclockwise method.

In deposition and in court you may be asked equations based on the traditional 90-degree quadrant method and may be called upon to demonstrate that the 360-degree method - the method you normally use - produces the same results as the traditional method. This article gives you what you need to know to handle such occasions with confidence.

You will learn to do the following in a way appropriate for the 90-degree quadrant method:

• Construct a coordinate diagram
• Measure angles within each quadrant
• Insert sine and cosine values for approach and departure angles
• Assign a positive (+) or negative (-) sign to each sine or cosine value
• Assign a positive (+) or negative (-) direction to each momentum
• Construct and use linear momentum equations

As you must be able to demonstrate that the equations used in the 90-degree method yield identical results to those obtained by use of the 360-degree left-hand method (because ultimately the equations for both methods turn out to be identical), you will learn to make equations for the 360-degree method as well.

You will see that although either method allows you to show Vehicle 1 approaching from either direction on the X-axis, an approach from right to left used within the 360-degree method requires you to insert the appropriate sign for each momentum direction, as in the 90-degree method, and you will be shown an easy way to do this.

Wiley Howell is a 24-year veteran of the Tampa (Florida) Police Department. After retirement, Mr. Howell established his own reconstruction business while teaching traffic crash courses at IPTM. He has been ruled an expert in both criminal and civil courts over several thousand times throughout his career as a police officer and in private enterprise.

Specifications: 42 pages; 8½”x11”; saddle stitched; illustrated with diagrams; Publisher: IPTM (1999)