Radioactive isotopes are often introduced into the body through the bloodstream. their spread through the body can then be monitored by detecting the appearance of radiation in different organs. 1311, a b- emitter with a half-life of 8.0 days is one such tracer. suppose a scientist introduces a sample with an activity of 375 bq and watches it spread to the organs. assuming that the sample all went to the thyroid gland, what will be the decay rate (activity) in that gland 24 days later? if the subject's thyroid has a mass of 20 grams, and each b- is of energy 5 kev, what is the total dose of radiation the thyroid receives?

Search coils and credit cards. one practical way to measure magnetic field strength uses a small, closely wound coil called a search coil. the coil is initially held with its plane perpendicular to a magnetic field. the coil is then either quickly rotated a quarter-turn about a diameter or quickly pulled out of the field. (a) derive the equation relating the total charge q that flows through a search coil to the magnetic-field magnitude b. the search coil has n turns, each with area a, and the flux through the coil is decreased from its initial maximum value to zero in a time ∆t. the resistance of the coil is r, and the total charge is q = i∆t, where i is the average current induced by the change in flux. (b) in a credit card reader, the magnetic strip on the back of a credit card is rapidly “swiped” past a coil within the reader. explain, using the same ideas that underlie the operation of a search coil, how the reader can decode the information stored in the pattern of magnetization on the strip. (c) is it necessary that the credit card be “swiped” through the reader at exactly the right speed? why or why not?

You are given a vector a = 125i and an unknown vector b that is perpendicular to a. the cross-product of these two vectors is a × b = 98k. what is the y-component of vector b?

Listed below are the measured radiation absorption rates (in w/kg) corresponding to 11 cell phones. use the given data to construct a boxplot and identify the 5-number summary. 1.16 0.85 0.69 0.75 0.95 0.93 1.18 1.17 1.42 0.54 0.57 the 5-number summary is nothing, nothing, nothing, nothing, and nothing, all in w/kg. (use ascending order. type integers or decimals. do not round.)