Approximately how many half-life periods must elapse if the activity of a radioactive isotope sample is to be reduced to 0.03 of the original value?
a. 5
c. 8
b. 3
d. 60
A
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Besides Earth, which of the terrestrial planets and/or satellites of terrestrial planets show(s) evidence for the possible existence of liquid water flowing on its surface in the past?
a. Venus b. The Moon c. Phobos d. Mars e. None of the terrestrial planets or satellites show such evidence.
Conduction: A heat-conducting rod that is wrapped in insulation is constructed with a 0.15-m length of alloy A and a 0.40-m length of alloy B, joined end-to-end. Both pieces have cross-sectional areas of 0.0020 m2. The thermal conductivity of alloy B is known to be 1.8 times as great as that for alloy A. The end of the rod in alloy A is maintained at a temperature of 10°C, and the other end of the rod is maintained at an unknown temperature. When steady state flow has been established, the temperature at the junction of the alloys is measured to be 40°C, and the rate of heat flow in the rod is measured at 56 W. What is the thermal conductivity of alloy A?
A. 120 W/m ? K B. 125 W/m ? K C. 130 W/m ? K D. 135 W/m ? K E. 140 W/m ? K
__________ is (are) observed when light from a distant quasar travels past a massive galaxy between us and the quasar, and this light is focused to form two or more images of the same quasar
a. A double-lobed radio galaxy b. Superluminal expansion c. The gravitational lens effect d. A blazar e. Gravitational waves
A plane flying horizontally at a speed of 50.0 m/s and at an elevation of 160. m drops a package of supplies. Two seconds later it drops a second package. How far apart will the two packages land on the ground?
A) 100. m B) 67.7 m C) 283. m D) 162. m E) 177. m