A60-g sample of radioactive isotope is measured after two half-lives have passed. what pair of percentages describes the sample after two half-lives? 50% unchanged and 50% stable 25% unchanged and 75% stable 12.5% unchanged and 87.5% stable 75% unchanged and 25% stable

It takes a lot of energy to get the temperature of water to increase and eventually boil because water has a high heat.

Why does magnet 5 float above magnet 4

Conventional hot-water heaters consist of a tank of water maintained at a fixed temperature. the hot water is to be used when needed. the drawback is that energy is wasted because the tank loses heat when it is not in use, and you can run out of hot water if you use too much. some utility companies are encouraging the use of on-demand water heaters (also known as flash heaters), which consist of heating units to heat the water as you use it. no water tank is involved, so no heat is wasted. a typical household shower flow rate is 2.50 gal/min (9.46 l/min ) with the tap water being heated from 51.0 ˚f (10.6 ˚c) to 120 ˚f (48.9 ˚c) by the on-demand heater. what rate of heat input (either electrical of from gas) is required to operate such a unit, assuming that all the heat goes into the water?