Human physiology aside, I wonder which device is more mechanically efficient, a bicycle or a unicycle?
[Physics] Which is more mechanically efficient, a bicycle or a unicycle
efficient-energy-use
Related Solutions
The question is quite complex, but there are several fairly simple things that can be observed:
First off, the standard bicycle, as a machine, is quite efficient. Very little energy is lost in the "drive train", with the vast majority of "lost" energy (mechanical energy input at the crank that is not converted to momentum) being expended as either air friction or friction between tire and roadway.
The human body, on the other hand, is often an incredibly inefficient machine. Not only are there simple concerns of "energy efficiency" -- how many calories of food, say, it takes to produce an erg of "work" -- but there are also major issues of "durability" and "endurance", both in the short term and long-term.
The average human body tends to have a "sweet spot" for cycling where the cadence is (depending on the individual and the circumstances) somewhere between maybe 60 and 90 RPM. Cycling within the "sweet" range for the individual produces a large amount of energy (though perhaps not the "peak" energy) and, more importantly, minimizes fatigue and optimizes endurance (as measured, say, in total energy produced in a given 24-hour period, including rest, eating, sleeping, etc).
In terms of gear ratio, in addition to determining cadence on relatively level ground, it also, of course, affects climbing. An individual is limited as to the total torque they can place on the bike crank arms, and hence what degree of incline they can climb at a given gear ratio. Lowering gear ratio (obviously) reduces the torque required to turn the crank arms and hence enables climbing a steeper incline. Here the "sweet spot" (for a relatively short climb) is below the level ground "sweet spot", but there still is one.
When considering cadence both on level ground and climbing it needs to be considered that muscles are more efficient when in "aerobic" mode -- burning "fuel" using oxygen supplied from the lungs via the bloodstream. Aerobic mode is perhaps twice as efficient as anaerobic mode (though don't quote me on that number), and, of major importance, it produces far fewer metabolic byproducts which can accumulate in the body and eventually become toxic. Although there are several factors that determine whether exercise is aerobic or anaerobic, a major one is, in fact, cadence, with lower cadences being more likely to be anaerobic.
The dehumidifier is probably more efficient.
When the wet clothes are drying, there is a latent heat of evaporation that will cool down the basement as the water evaporates. You then have to run the dehumidifier to cause this water to condense again - in the process you will heat the room (as you expel the excess heat). In principle, no heat leaves the building.
If you run the dryer, you expel a lot of hot moist air to the outside world.
Just considering those two closed systems, the dehumidifier should be the better option. Whether it actually is for you depends on other factors: how much running the dehumidifier heat the basement, and where does that heat end up going?
Best Answer
According to Wikipedia:
Given that on a unicycle, there is no chain, it ought to heave fewer losses in the transmission system between foot and road.
However, if you look at overall efficiency of the whole human plus bicycle system for a specific activity, a conventional geared bicycle may be a more efficient means of transport due to gearing, the availability of brakes and other factors. Human pedalling efficiency is best when the person maintains an optimal pedalling cadence. This might be more difficult on a cycle that has no gears. At a minimum, the unicycle will have only one optimal speed where a geared cycle has many.