Quick Conceptual Question about Energy

[bcjochim07]

Homework Statement

A system loses 400 J of potential energy. In the process it does 400 J of work on the environment and the thermal energy increases by 100 J. Show this process on an energy bar chart.

Homework Equations

Ui + Ki + Wext = Uf + Kf + change in thermal energy

The Attempt at a Solution

I drew a bar with value +400 J for Ui, +100 J for Ki, and -400 J for Wext. Then I drew a bar of +100 J for change in thermal energy. The part I'm not sure about is the +100 J for Ki since the problem doesn't say anything about losing kinetic energy. But that was only way I could think to make the equation balance.

Any thoughts would be greatly appreciated.

 

[anathema]

Hi there,

Your solution is correct! The +100 J for Ki represents the initial kinetic energy of the system, which remains unchanged throughout the process. It is important to include it in the energy bar chart to show that the system's total energy (potential + kinetic) is conserved.

Great job on using the energy conservation equation to solve this problem. Keep up the good work!

 

[Moetasim]

Your attempt at a solution is correct. The 100 J for Ki represents the initial kinetic energy of the system, which remains constant throughout the process as there is no mention of any changes in velocity or motion. Therefore, the equation balances out with the initial kinetic energy being equal to the final kinetic energy. Keep up the good work!