Physics of Dog Mushing

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Acceleration/Velocity

Acceleration and velocity are mostly dependent on the number of dogs, the quality of the dogs, and how well the dogs have been trained, but it also can depend on friction and inertia. The lager mass an object has the the more weight it has and the more inertia it has.

Weight effects acceleration by increasing friction. Friction is f = µN where µ is the coefficient of friction, N is the normal force, and f is friction. The normal force is equal to mass times gravity assuming no other downward forces are applied. Therefore the more weight in both sled gear and musher the dogs have to haul the lower the velocity and the slower the acceleration will be due to friction between the runners and the ground.

Inertia effects acceleration because inertia is the tendency of objects to ether stay at rest or stay in motion. In this case since the point is to move we are more concerned about staying at rest. When starting the dogs have to pull harder to get the sled moving then they do to keep it moving to both overcome the effects of inertia and to change the fiction from static friction to kinetic friction.

Force/Work

Force is necessary to start all motion, and in the presence of friction force is needed to maintain a constant velocity. In mushing a vast majority of the force comes from the dogs, and depending on the musher as a small amount to no force comes from the musher (assuming flat terrain).

Mathematically F = ma where "F" is force, "m" is mass, and "a" is acceleration. this tells us that if the velocity is constant then the sum of the forces equals 0(F = 0). this doesn't mean the dogs aren't applying any force it just means that they are only applying enough force to over come any friction that might be resting the forward motion.

The dogs apply this force by pulling on the tug lines which leads to a gangline which is attached to the sled. some mushers place a shock absorber between the sled and the gangline to both ease jolts from the dogs accelerating from a stop and to reduce the jolt on the dogs from large bumps in the trails.

Work

The dogs are only doing work when they are accelerating because W = Fd where W is work, F is force, and d is distance.

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