Karate - Board Breaking

By: Katie Polakowski and Amanda Lopez
High Speed Video
Link to Download Video

Image from Tracker

Position Graph of Right Hand
 The velocity of the right hand is -7.23 at the point when it hits the board.
Velocity Graph of Right Hand (when hand hits the board)
Was there constant velocity? If so, how do you know?
There was not constant velocity because Amanda's right hand starts out slower and as it got closer, the velocity dramatically increased. After her hand breaks the board, the velocity greatly decreases.
This is a picture from Tracker where Amanda's hand is at the highest velocity.
How did the velocity change? Why does velocity change?
Velocity is small at first, but then it dramatically increases to -11.65 m/s right before her hand hits the board. Then, after she breaks the board, the velocity decreases a lot. The velocity changes because a greater velocity is needed to break the board. It decreases because the break has been completed and she is stopping her hand.
Acceleration Graph of Right Hand
Is there acceleration? Is it constant?
There is acceleration because velocity is not constant. The velocity increases over time, which gives us an acceleration. The acceleration is not constant, however. We know acceleration is not constant because the velocity graph is not increasing at a steady rate, therefore it is not a diagnol line.
Acceleration Graph up to Breaking Point
Acceleration Graph with Area Up to Break
Does area under your acceleration graph equal the change in velocity you read from your data table?
Yes, the area is close to the change in velocity. The change in velocity is 9.4 - 7.1 = 2.3
The area under the acceleration graph equals 1.97

Steve Dickie,
Oct 27, 2009, 12:22 PM