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How the Obstacle Works
The weave poles are a series of poles standing perpendicular to the ground through which a dog must weave. There are specific rules concerning how the dog must enter, but the concept of this event is quite simple. However, this event combines speed and tight turns, using physics to create what some consider the most challenging obstacle.
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Newton's First Law (Law of Inertia)
Newton's First Law states that an object will maintain its current velocity unless acted on by an outside force. This law of motion also deals with inertia, or an object's resistance to any change in velocity. Although inertia is never seen with a number amount, the more mass an object has, the more it resistance and inertia it has. All aspects of this law are clearly acting in the weave pole event. For example, the dog will start the task by running in between the first two poles, but then will need to quickly change its direction, and therefore its velocity, to navigate through the next set. Overpowering the inertia takes a lot of effort from the dog, especially when repeated, and dogs with more mass will have a harder time completing this task. This is why many dogs try to keep their torso from moving back and forth as much as possible. The less they can switch directions, the easier it will be to go fast.
The Dog's Momentum
Momentum also can greatly affect the way a dog completes the weave pole obstacle. In reference to the formula on the right, we can compare the performance of two (imaginary) dogs with different masses ; Scruffy weighs 12 kilograms and Patches weighs 6. If these dogs were to both have the same change in velocity as each other (4 m/s^2), we could use the formula and see that Scruffy would end up with a greater change in momentum. However, both sides of the formula need to balance out. When compared to Patches, Scruffy would need to either raise the amount of force put in or the time to achieve the correct amount of impulse. Because the goal is to achieve the quickest time, Scruffy would need to put in more force than Patches to get the same results (2 seconds), proving the effect momentum has on this event. After solving for the force, we learn that Scruffy needs double the force to achieve the same time as Patches.
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Force*time=mass*change in velocity
Scruffy needs more force than Patches!
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