4 ms·

I don’t know why you’re getting downvoted. 1kW is a microwave, and 1GW is a nuclear power plant. It seems not unreasonable to expect people to understand this.

bsder 7y ago
Maybe, but the fact that a high end commercial microwave is about the same amount of power as my car rolling along at about 30mph(45kph) on a level road would have surprised my intuition initially. I would have pegged a car for MUCH higher power output. So, while I probably wouldn't have pegged a dragster at GW, I might have pegged it at 50-200MW assuming I put my car at an incorrect 200kW on average as opposed to top end (assuming a dragster is at least 100x a bog standard car wouldn't be out of bounds). In addition, assuming that a dragster has an instantaneous (or short lived) power output on the same level as a diesel power plant (designed to be continuous) probably also isn't out of whack. My estimates are still hilariously out of whack--simply because my errors are compounding in the same direction. I have had this happen at other times. RF level strength loss due to antennas is one of those. I was hunting a problem and saw the signal but something like -90dbm down. I mumbled that "Wow, did we get our antenna match that wrong?" An experienced RF engineer looked at me and laughed "If you have an antenna that can actually kill a +20dbm signal to better than -90dbm, you should patent it. Check the firmware. Power amp probably isn't turned on." He, of course, was completely correct because he knew that killing an RF signal more than 50dbm or so gets really hard.
- sampo 7y ago
  A car driving 100 kph (62 mph) on a highway, uses 2 or 3 ml (0.07 to 0.1 US liquid oz) of gasoline per second. That sounds also like about the size of a fire that you can use to heat up food.
  - projektfu 7y ago
    Interesting. A US gallon per hour is roughly a milliliter per second.
  - userbinator 7y ago
    100km/h ~ 30m/s 3cm^3/s / 30m/s = 3cm^3/s / 3000cm/s = 0.001 cm^2 = 0.1mm^2 Fuel efficiency can be measured as an area, and 0.1mm^2 corresponds to approximately 30mpg. See https://news.ycombinator.com/item?id=9504215 https://news.ycombinator.com/item?id=9504215
- perl4ever 7y ago
  "Maybe, but the fact that a high end commercial microwave is about the same amount of power as my car rolling along at about 30mph(45kph) on a level road would have surprised my intuition initially. I would have pegged a car for MUCH higher power output." Well, I think most people don't have an intuition for whatever a "high end commercial microwave" is. I would expect a car on a level highway to be using on the order of 10 hp. I'm sure my microwave uses far less.
  - labawi 7y ago
    Air resistance is proportional to speed squared, meaning (air resistance component of) energy per distance is ~ speed², and energy per second is ~ speed³. 45 km/h vs. 90 km/h is almost an 8-fold difference of power to sustain. Air resistance is not the dominant factor on lower speeds, so I'd guesstimate it at 6-7x. At 130km/h, with 33.6 MJ/l gasoline energy content, at 7l/100km, you get: 9.1l/h -> 300 MJ/h -> 84kW. At 30% efficiency you get 25kW or 33hp. That's about a dozen microwaves. At 45km/h, air resistance power use should be about 1/24 of 130km/h. Guesstimating total consumption as 1/10, you get around 2kW, or a single (240V 10A) microwave/kettle.
    - perl4ever 7y ago
      Going at a steady 30 mph on a straight, level road is not really something people do in my part of the world, so I can't say that I have experience to know what sort of gas mileage you'd get. Edit: More research suggests that gas mileage should be similar between 30 and 60 mph, it kind of plateaus, but I guess that means power required would still go up proportionally. 10 hp is something I was remembering from reading something about driving at around 60, so I guess 30 mph should take 5 hp.
      - mrguyorama 7y ago
        In about the 80s, cars were rather more efficient at 50mph. Depending on brand, market segment, and transmission, I'd believe they are roughly as fuel efficient at higher speeds. My car (2.0L turbocharged hatchback) uses about 7-14kw to maintain 60-70mph on level ground at around 30-33mpg. The unfortunate uncertainty in my figures is due to poor memory

bsder 7y ago

Maybe, but the fact that a high end commercial microwave is about the same amount of power as my car rolling along at about 30mph(45kph) on a level road would have surprised my intuition initially. I would have pegged a car for MUCH higher power output. So, while I probably wouldn't have pegged a dragster at GW, I might have pegged it at 50-200MW assuming I put my car at an incorrect 200kW on average as opposed to top end (assuming a dragster is at least 100x a bog standard car wouldn't be out of bounds). In addition, assuming that a dragster has an instantaneous (or short lived) power output on the same level as a diesel power plant (designed to be continuous) probably also isn't out of whack. My estimates are still hilariously out of whack--simply because my errors are compounding in the same direction. I have had this happen at other times. RF level strength loss due to antennas is one of those. I was hunting a problem and saw the signal but something like -90dbm down. I mumbled that "Wow, did we get our antenna match that wrong?" An experienced RF engineer looked at me and laughed "If you have an antenna that can actually kill a +20dbm signal to better than -90dbm, you should patent it. Check the firmware. Power amp probably isn't turned on." He, of course, was completely correct because he knew that killing an RF signal more than 50dbm or so gets really hard.

sampo 7y ago
A car driving 100 kph (62 mph) on a highway, uses 2 or 3 ml (0.07 to 0.1 US liquid oz) of gasoline per second. That sounds also like about the size of a fire that you can use to heat up food.
- projektfu 7y ago
  Interesting. A US gallon per hour is roughly a milliliter per second.
- userbinator 7y ago
  100km/h ~ 30m/s 3cm^3/s / 30m/s = 3cm^3/s / 3000cm/s = 0.001 cm^2 = 0.1mm^2 Fuel efficiency can be measured as an area, and 0.1mm^2 corresponds to approximately 30mpg. See https://news.ycombinator.com/item?id=9504215 https://news.ycombinator.com/item?id=9504215
perl4ever 7y ago
"Maybe, but the fact that a high end commercial microwave is about the same amount of power as my car rolling along at about 30mph(45kph) on a level road would have surprised my intuition initially. I would have pegged a car for MUCH higher power output." Well, I think most people don't have an intuition for whatever a "high end commercial microwave" is. I would expect a car on a level highway to be using on the order of 10 hp. I'm sure my microwave uses far less.
- labawi 7y ago
  Air resistance is proportional to speed squared, meaning (air resistance component of) energy per distance is ~ speed², and energy per second is ~ speed³. 45 km/h vs. 90 km/h is almost an 8-fold difference of power to sustain. Air resistance is not the dominant factor on lower speeds, so I'd guesstimate it at 6-7x. At 130km/h, with 33.6 MJ/l gasoline energy content, at 7l/100km, you get: 9.1l/h -> 300 MJ/h -> 84kW. At 30% efficiency you get 25kW or 33hp. That's about a dozen microwaves. At 45km/h, air resistance power use should be about 1/24 of 130km/h. Guesstimating total consumption as 1/10, you get around 2kW, or a single (240V 10A) microwave/kettle.
  - perl4ever 7y ago
    Going at a steady 30 mph on a straight, level road is not really something people do in my part of the world, so I can't say that I have experience to know what sort of gas mileage you'd get. Edit: More research suggests that gas mileage should be similar between 30 and 60 mph, it kind of plateaus, but I guess that means power required would still go up proportionally. 10 hp is something I was remembering from reading something about driving at around 60, so I guess 30 mph should take 5 hp.
    - mrguyorama 7y ago
      In about the 80s, cars were rather more efficient at 50mph. Depending on brand, market segment, and transmission, I'd believe they are roughly as fuel efficient at higher speeds. My car (2.0L turbocharged hatchback) uses about 7-14kw to maintain 60-70mph on level ground at around 30-33mpg. The unfortunate uncertainty in my figures is due to poor memory