Each time you dumped the pennies, one half-life passed; it has been shown that the half-life for this radioactive isotope is 20 years
in the year 2000, an archaeology team unearths pottery and is using this isotope for radiometric dating to place the age of the pottery
it is shown that 95% of the nuclei have decayed
approximately how long ago was the pottery made?

An internally reversible refrigerator has a modified coefficient of performance accounting for realistic heat transfer processes of where qin is the refrigerator cooling rate, qout is the heat rejection rate, and is the power input. show that copm can be expressed in terms of the reservoir temperatures tc and th, the cold and hot thermal resistances rt,c and rt,h, and qin, as where rtot rt,c rt,h. also, show that the power input may be expressed as 1.39 a household refrigerator operates with cold- and hot-temperature reservoirs of tc 5 c and th 25 c, respectively. when new, the cold and hot side resistances are rc,n 0.05 k/w and rh,n 0.04 k/w, respectively. over time, dust accumulates on the refrigerator’s condenser coil, which is located behind the refrigerator, increasing the hot side resistance to rh,d 0.1 k/w. it is desired to have a refrigerator cooling rate of qin 750 w. using the results of problem 1.38, determine the modified coefficient of performance and the required power input w under (a) clean and (b) dusty coil conditions. internally reversible refrigerator qout qin w high-temperature reservoir low-temperature reservoir th th,i tc,i tc high-temperature side resistance low-temperature side resistance w qin th tc qinrtot tc qinrtot copm tc qinrtot th tc

Asmall object with mass 0.200 kg swings back and forth on the lower end of a light rope that is 3.00 m long. the upper end of the rope is attached to the ceiling. as the object swings through its lowest position, where the rope is vertical, the speed of the object is 5.80 m/s. at this point in the motion, what is the tension in the rope? (use g = 9.80 m/s2.)

Which of the following statements are evidence that gases do not always behave ideally? check all that apply.? a. co2 gas becomes dry ice (solid co2) at 1 atm and –78.5 °c. b. when two gases are mixed, they follow dalton\'s law of partial pressures. c. at 4 k and 1 atm, helium is a liquid. d. it is impossible to compress a gas enough so that it takes up no volume.