# Search results

1. ### Why gyroboards are said to run so long on one battery charge...

My scooter powered by 24V 7AH battery, the (brushed) motor 250 W runs 4 mi. I have added more 7AH batteries (so 14AH now), so am having now 8 mi range. But how on earth anything powered 48V 4.4AH, the (even brushles) motor 700W could run 10 mi (let alone 13mi) ?
2. ### Why gyroboards are said to run so long on one battery charge...

Hello Ads say a gyroboard with the battery 48V 4.4AH, and the motor 700 Wt will run for 2 hours at the speed of 20km/h ! But - simple physics - will not the motor drawing about 10-15 Amp exhaust the battery in just some 20 minutes !? Do ads lie ?
3. ### Mercury in air

Exposure or Absorption and the Crucial Question of Limits for Mercury Derek W. Jones, PhD, FIM, CChem., FRSC(UK), FBSE ABSTRACT
4. ### Mercury in air

Who knows what is safe amount of inorganic mercury breathed daily ?
5. ### Mercury in air

2 statements from an article : "WHO standards for occupational exposure to inorganic mercury are currently 50 µg/m3 in air ...... WHO's maximum acceptable daily intake (ADI) for mercury is 40 µg/day." An average person inhaling 20 m3 of the air containing 50 µg/m3 of mercury, inhales...

Thank you.
7. ### Water density / volume

But will % of expansion = % of decrease in density ?
8. ### Water density / volume

Let it be it, but I refer to the exactly 2 points (on the "curve") between which there is the 4% decrease in density for, as it seems, 2% increase in volume Square root ?
9. ### Water density / volume

I mistakenly put it otherwise so, more precisely - according to the reference - it should be : 0.999808 at 0 °C 0.958593 at 100 °C - about 4 % of the initial value But the volume will increase just 2 % Maybe there is square root relation ?
10. ### Water density / volume

Water density at 0 C is 990 kg/m3. Water density at 100 C is 1030 kg/m3 - 1 m3 of water "loses" about 4 % of its mass. Water expansion rate is 1.0002 for each 1 C increase in temperature - 2 % for the above rise from 0 C to 100 C.. How comes that water density decreases 4 % but its volume...
11. ### Measurement points for fan performance curve

Volume. Should turbulence in some points of the duct add some dynamics to static pressure being measured by the probe placed right perpendicular to flow ?
12. ### Measurement points for fan performance curve

For finding fan performance curve where better to put static pressure probes - near the surface or near the center of the duct ?
13. ### Homomorphism between Lie groups

It's mathematics not physics !
14. ### Water as coil core

I need to empty an actually water glycol-system but I do not want to remove all but to a certain level. It would be an improvised level sensor.
15. ### Water as coil core

water as coil "core" How much a coil inductance of 0.1 mH (3 cm long, some 50 turns wound around 5 cm diameter empty plastic pipe) may change when water enters the pipe ?
16. ### The capillary action's limit

: ".........venerable question of why sap rises in tall trees [32]. We hope to address this problem in future work"

18. ### Oil boiling point at vacuum

Millitorrs are generally called "microns". It is assumed among refrigeration engineers that during vacuumation processes the oils in systems worked upon, themselves, do not boil - no matter how high vacuum would be achieved. I am in doubt.
19. ### The capillary action's limit

I meant artificial material.
20. ### Water evaporation

Water evaporates slowly at all temperatures, and the evaporation increases with water temperature increase, but the "boiling" starts at the point the water temperature reached 100 degrees Celsius at atmospheric pressure.
21. ### The capillary action's limit

Is it feasable to achieve elavation of water to, let's say, 10 m height due to the capillary action effect ? Or the capillary diameter for that to achieve should be less than the water molecules themselves ?
22. ### Oil boiling point at vacuum

What may be the boiling point (temperature) of a refrigeration POE oil at, let's say, 500 microns absolute pressure ?
23. ### Directing dangerous objects to Sun

So, it is all not so simple as I thought. Thank you !
24. ### Partial pressure

It is not chemistry but rather physics.
25. ### Directing dangerous objects to Sun

I meant asteroids endangering the Earth against which many sorts of weaponry are discussed (and probably designed and build).
26. ### Partial pressure

Do you mean it is over 15 B ?
27. ### Heat Transfer into a heat reservoir

Please note that temperature will change the resistance of the conductor.
28. ### Directing dangerous objects to Sun

I have never heard about a plan of cosmic objects endangering Earth to be directed towards the Sun in order to get rid of them. It is unfeasable ? "Sun wind" blowing from the star is stronger than its gravitation ?
29. ### Partial pressure

Am I assuming right the pressure in a vessel holding two substances (both being in the both liquid and gas states) will be equal to the saturation prerssure of the one which has the higher SP ? That is, for substance A whose SP at a given temp. is 10 B, for instance, and substance B whose SP is...
30. ### Ac lagging

You are correct. It is always assumed so as you say, but in reality the "loss in copper" current starts immediately the emf is applied. What is form of the current on oscilloscope ? (I have never had an access to one) A slope of the resistive current, then the sine of the magnetizing current...