## SPS Zone 5 Home Page: Student Abstracts III

### SPS Zone 5 Home Page

**High Speed Video Analysis of Force by a Bowstring on an Arrow**

Brielle Spencer (High Point University)

Bows and arrows have been used for years for both hunting and recreational purposes, and over time innovations have been made to the bow to make it easier for the user. An arrow needs to have high force on it in order to accelerate to high speed, but the user must also be capable of drawing back and easily holding the string in this position. The purpose of this project was to analyze the force by a bowstring on a Mathews Solocam Bow on an arrow as it is shot. Using high-speed video analysis, the net force on the arrow was measured, and a force versus distance graph was analyzed to determine how the force varies as a function of distance while the arrow is in contact with the string. The data showed three distinct regions: (1) an initially rapid increase in the force (just after the arrow is released), (2) a nearly uniform, linear increase, and (3) a nearly constant force that acts for more than half the distance traveled before the arrow leaves the bow. This is consistent with the design of the bow that when drawn is initially difficult to pull, becomes easier to pull, and then becomes very easy to hold when fully drawn.

**An Alternative Numerical Technique for Calculating the Perpendicular Component of the Net Force on an Object**

Catherine Hendricks (High Point University)

According to Newton's second law, the net force on an object is equal to the time rate of change of the object's momentum. The perpendicular component of the net force on the object changes the direction of the momentum and the tangential component of the net force changes the magnitude of the momentum. For motion of an object along any curved path, a numerical technique to calculate the perpendicular component of the net force based on a best-fit circle at a point on the object's path is being investigated. This numerical technique and approximations will be discussed along with a comparison of its results with what is obtained from a numerical derivative of the momentum vector.

**Accounting for Non-Constant Thrust in a Model Rocket Simulator**

Elizabeth Messina (High Point University)

Model rocket simulators usually account for the thrust of the engine by assuming it is constant. However, in reality the force is not constant. The purpose of this project is to determine the thrust curves of various model rocket engines by measuring the thrust vs. time and fitting an eight-parameter function to the data. The thrust curves were used in a model rocket simulator developed with Easy Java Simulations (EJS) and results were compared with the case of constant force.

**High-Speed Video Analysis of Karate Kicks**

Laura Lee (High Point University)

A properly performed karate kick requires agility and balance to produce a maximum-speed kick during the largest possible range. In this project, high-speed video analysis at 300 fps was used to study three different kicks: (1) the front kick, (2) the side kick, and (3) the roundhouse kick. The front kick was found to produced the maximum speed in the shortest amount of time. In each case, the maximum speed plateaued for a brief time interval, producing an optimal range in which to strike the target. Videos, graphs, and data analysis or the three different kicks will be presented.