Janis volunteered to participate in a psychology experiment. when she arrives at the lab a lab assistant standing on the other side of a counter greets her. the lab assistant explains the informed consent procedure and asks her to sign the form. as the lab assistant reaches for the form he drops it behind the counter. he drops down behind the counter to pick up the form, but, unbeknownst to janis, another person stands up holding the form. after janis signs the form, she is asked if she noticed the change. she replies that she did not. this phenomenon is known as:

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?