I was taught in my Physics lessons that the hotter an object is, the quicker it looses heat. My plumber reckons that it's cheaper to keep the hot water on all day rather than heat it and let it cool if it's not used. What's the better way? Keep the water hot, or let it cool, and then heat it on demand?  

hi

I want know how i can explore variable and make Bayesian Network in a Data Criminal profile?

help me

tanks a lot

 I made some pasta sauce with meatballs.When it came out of the microwave, the meatballs had arranged themselves perfectly.

The meatballs are quite small and are not touching under the surface

Any ideas what caused this?

I have, for most of my life been confronted with shoveling snow from our sidewalk  in winter.  We have used up many different snow shovels - sometimes getting wider ones, shorter ones, different handled ones.  But one thing remains true about all of them - they all wear away over time but in the same pattern.  A protrusion at one end, a sweeping outward curve to the middle then the pattern repeats to the other side.  The least abrasion occurs at the point where all the pressure is applied.

If I keep a plastic mineral-water bottle topped up with tap water and regularly drink directly from it, the neck smells vile after a couple of weeks. Why is this and why is it always exactly the same smell?

My daughter dived underwater in the swimming pool and screamed as loud as she could. I was right next to her with my head out of the water, but I could only detect the tiniest sound, at the end of the scream. But when I was underwater with her, I could hear most of the scream. Why?

A Light Dependent Resistor(LDR) could be used in certain electronic circuits as an automatic switch along with a transistor. It works on the principle that the resistance in the circuit is inversely proportional to the light intensity, thus implying that the resistance increases as the vicinity gets darker, triggering a flow of current. I believe this has something to do with the photoelectric effect, but could someone please explain the correlation between the resistance and the light intensity as well as why an increase in the resistance triggers the flow of current and not the other way around(i.e a decrease in resistance triggering a flow of current)?

Is it better to stay up late on the night before an exam, learning those last-minute facts, or to get up early and revise in the morning before the exam?

When I open a new jar of marmalade the contents are a nice, semi-solid, homogenous mass with a smooth surface, however old the jar is. Yet when I make a spoonful-sized hole in the flat surface to remove some marmalade, the next time I open the jar a couple of days later, the hole has started to fill with a syrupy liquid. What is it about breaking the surface of the marmalade that sets this process in motion? It continues until the jar is empty.