Could this device theoretically continue in motion forever? If not, why not? (click below for images):
- The device is less dense than air, so it rises. The propeller spins slightly (maybe) charging the device battery.
- After rising some distance X, the device compressor turns on to deflate the device.
- The device becomes more dense than air and falls quickly spinning the propeller, charging the battery.
- After falling X, the compressor releases and the device becomes less dense than air, going back to step 1.
The logic here is that there must be some distance X that the device can rise than will generate more energy than what is needed by the compressor.
Here is the underlying math to help:
PE = mgh
- m = mass of the device
- g = coefficient of gravity
- h = height device has traveled up
- PE = potential energy of the device as it travels up
CW = nRT(ln(Vb) - ln(Va))
- n = number of moles of gas in balloon of device
- R = ideal gas constant
- T = temperature of the gas
- Vb = volume of the balloon after compression
- Va = volume of the balloon before compression
- CW = work to compress the balloon
As h increases PE increases but CW stays the same resulting in energy gain of the system.