The unstable isotope 234Th decays by ? emission with a half-life of 24.5 days. The initial decay rate of the sample was 9.9 × 1013 Bq. (1 u = 1.6605 x 10-27 kg)
(a) What mass of 234Th was initially present?
(b) What is the decay rate after 68 days?
(a) 0.12 g (b) 1.4 x 1013 Bq
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A single-shell-eight-tube-pass heat exchanger is used in a power plant to preheat 55ºF water to 80ºF by using 190ºF hot water and cooling it to 160ºF. If the overall heat exchanger conductance is 400 Btu/hr?ft^2 ?0F and if 1800 lbm/min of 55ºF water is preheated, determine (a) mass flow of the hot water and (b) surface area of the heat exchanger.
What will be an ideal response?
The light from Polaris is 24.2 times less intense than the light received from Sirius. Which star is the truly brighter star, that is, emitting more visual light at its surface?
a. Polaris b. Sirius c. Neither, they emit the same amount at their surfaces. d. This cannot be determined based upon the information given.
The scarps on Mercury are extremely similar to the cratered lunar highlands in appearance
Indicate whether the statement is true or false
Explain the relationship between velocity and acceleration
What will be an ideal response?