Today is the final day of Blogmas. For this very special day, I will find the frictional force of a child riding on sled. The average mass of a 10 year old child is 31.9 kg. To find the normal force I multiplied the acceleration due to gravity by the mass of the child and got 312.62N. The coefficient of between snow and plastic is .3, so the force of friction is between the sled and the ground is 93.786N.