12
Three seconds.
Not that you could measure. A fan should reach a stable speed in just a few seconds.
They say to be about 3 seconds behind the person infront of you. So the faster you move the further back you should be.
A sophomore in high school should be able to run something in the low 15 sec range.
slower and harder slower and harder
There is definitely faster out there but for home use it is very good. Most web pages will open within 1-2 seconds completely and videos should load faster than they play, thus, no buffering issues.
contrails are water molecules at high altitude due to condensation.
your asking for an opinion...
You should replace or compensate for the loss. You would expect no less.
This depends on the aerodynamic shape, weight, size of your vehicle. The optimal speed for fuel economy will be faster for a low to ground, relatively pointed shaped vehicle as compared to a van or SUV. Generally speaking, if you are driving faster 65 mph, you are probably burning more gas to compensate for the increased wind resistant.
If you see the him/her, the cyclist will probably only be a few seconds away. Let him/her pass first - then open the door.
You should get a sufficintly accurate indication after 10 seconds and, that way, you save a whole 50 seconds!