# Is Work Always the Transfer of Energy?

1. Dec 5, 2012

### curiously33

Is work always the transfer of energy?

This wasn't in any homework, but I've tried asking various teachers and searching the internet, and I can't find any definitive answer. I'm currently learning about work in Grade 11 Physics, and I was wondering. I know that work is a force acting over a distance, but if a soccer ball, for example, is travelling through the air, there is no contact, and therefore no transfer of energy. However, work is still being done. I know that it has kinematic energy due to it's motion, but there is no transfer of energy.

2. Dec 5, 2012

### rock.freak667

There is transfer of energy. The ball will initially have kinetic energy as it is kicked. As it rises through the air, some of that energy is converted into gravitational potential energy and some is converted to heat (due to friction with the air it is moving through).

3. Dec 5, 2012

### curiously33

Oh. I see. Thank you for the clarification. Another question: I thought potential energy was just a concept rather than an actual property. Is that not the case?

4. Dec 5, 2012

### PhanthomJay

Change in potential energy is what is important, but that still does not imply that potential energy by itself is just a concept. A brick on a roof has potential energy with respect to the ground, but none with respect to the roof. But you can say the same thing about kinetic energy: a moving object has kinetic energy with respect to a stationary observer, but has no kinetic energy with respect to an observer moving at the same speed as the object. In both cases, however, it is work that causes the change in energy. Its all relative, you know.