Work and Energy - Mission WE7 Detailed Help

A sledder effortlessly glides from position A across the snow to position B (as shown in the diagram below). Resistance forces are negligible. At position B, the total mechanical energy of the sledder is _____ Joules and the kinetic energy is ____ Joules.

Work - Mechanical Energy Relationships:
If non-conservative forces do net work upon an object, then the total mechanical energy of that object is changed. The sum of the kinetic and potential energies will change as work is done upon the object. If non-conservative forces do NOT do net work, then the total mechanical energy will be conserved.

Definition of Total Mechanical Energy:
The total mechanical energy possessed by an object is the sum of its kinetic energy and potential energy.

The sledder is gliding effortlessly; resistance forces are negligible. The only forces doing work upon the sledder is the force of gravity. So the mechanical energy of the object is conserved. It is the same initially as finally. See Know the Law section.
Mechanical energy takes two forms - kinetic and potential. The total amount of mechanical energy is simply the sum of these two amounts (see Dictionary section). At any given location along the path of the sledder, the total mechanical energy can be determined by adding the kinetic energy and the potential energy. If mechanical energy is said to be conserved, then the sum of the two forms - KE and PE - will be the same at any given location along the path of the sledder. If the total amount is known and the PE is known, the KE can be quite easily calculated.


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