Chapter 13, Problem 87PP

Physicians and physiologists are interested in the long-term effects of apparent weightlessness on the human body. Among these effects are redistribution of body fluids to the upper body, loss of muscle tone, and overall mass loss. One method of measuring mass in the apparent weightlessness of an orbiting spacecraft is to strap the astronaut into a chairlike device mounted on springs (Fig. 13.39). This body mass measuring device (BMMD) is set oscillating in simple harmonic

FIGURE 13.39 Astronaut Tamara Jernigan uses a body mass measuring device in the Spacelab Life Sciences Module (Passage Problems 87-90).

motion, and measurement of the oscillation period, along with the known spring constant and mass of the chair itself, then yields the astronaut’s mass. When a 60-kg astronaut is strapped into the 20-kg chair, the time for three oscillation periods is measured to be 6.0 s.

If the same device were used on Earth, the results for a given astronaut (assuming mass hasn’t yet been lost in space) would be

1. a. the same.
2. b. greater than in an orbiting spacecraft.
3. c. less than in an orbiting spacecraft.
4. d. meaningless, because the device won’t work on Earth.