How much Energy Does it Take to Sled?

         That is a good question. How much energy is needed to get to the top of the hill and to get back down? First, you have to walk up to the top of the hill. Once you get to the top, however high it is, you now have potential energy. Potential energy is defined as "the energy associated with the configuration of a system of objects that exert forces on each other" (Serway and Jewett pg. 218). Only gravitational potential energy is going to be discussed here. The gravitational potential energy is the energy from an object that is released from a certain height, which then the energy is converted into kinetic energy when it is released.  Gravity does work on an object when it falls or rises. The work equation (W=F*d) becomes the potential energy equation U=mgy where U is potential energy, m is mass, and y is the height the object traveled.
        When an object begins to fall, its potential energy is converted into kinetic energy. The further the object falls towards the ground the potential energy decreases more and more, while the kinetic energy increases more and more. The kinetic energy of an object is K=1/2mv² where m is mass and v is velocity. Kinetic energy is the energy associated with a moving object. The drawing below may help to show what is going on.

       
Drawn By Ryan Boothe

          These photos below of a skier base jumping and the other one is falling during dusk, shows an example of potential and kinetic energy. The vertical gain that the skiers have above ground is potential energy which is at the same time being converted to kinetic energy. The skier's velocities are increasing the further down they travel.  There are not any non conservative forces acting the the skier, such as friction and ignoring air resistance, so energy should be conserved.

                                       
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1. Back to Main Page
2. The Projectile Motion of a Sled off a Jump
        3. The Mechanics of Sledding          
4. How Much Energy Does it Take to Sled?
5. Bibliography