This is a picture from when we went dog sledding. In the picture, the dogs are at rest, but they quickly accelerated to a much faster velocity once they started running. The sled accelerated when it went around the curves in the trail because there was a change in direction. The mass of the sled and its passengers also affects acceleration and velocity. I rode twice, and I found that the sled went faster the first time because there was less people in it. The mass of the dogs and its cargo is also important to the momentum of the sled. The faster the sled is traveling and the heavier mass it has, the harder it is to stop.