Acceleration/Velocity   Sled 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.