AccelePrep for the ACT Test 2nd Edition Student Text

C HAPTER 11 | H YPER P REP S CIENCE • 209

7. In the presented set of experiments, only the effects of temperature and food intake on the mother are known; nothing is known about the offspring at all. Even though it might be reasonable to suppose that some of the extra food goes to the infant, there is no information provided that would back that idea. Therefore, neither (A) nor (B) is correct. In order to decide between (C) and (D), look for a data trend in the table that relates the mother’s birthing age to food intake: the age of the mother increases with decreasing food intake, (C).

POWER PRACTICE 1 DIRECTIONS: The passage below is followed by several items. After reading the passage, choose –Š‡ „‡•– ƒ•™‡” –‘ ‡ƒ…Š ‹–‡Ǥ ‘— ƒ› ”‡ˆ‡” –‘ –Š‡ ’ƒ••ƒ‰‡ ƒ• ‘ˆ–‡ ƒ• ‡…‡••ƒ”›Ǥ ‘— ƒ”‡ permitted the use of a calculator. Answers are ‘ ’ƒ‰‡ ͵ͳͳǤ An object in periodic motion, such as a mass on a spring or a pendulum, vibrates about a ϐ‹š‡† ’‘•‹–‹‘ ‹ ƒ ”‡‰—Žƒ” ƒ† ”‡’‡ƒ–‹‰ ˆƒ•Š‹‘Ǥ There are two measurable quantities of periodic motion: amplitude and period. The amplitude is the maximum displacement of the object, in either direction, from its resting position. The period is the time it takes the object to complete one cycle of motion: from resting position through the maximum

displacement on both sides of the resting position and then back to the resting position. Note that the period does not depend on how far the spring is initially stretched. This independence is a key feature of all systems that undergo periodic motion. A student investigates the relationships between position, velocity, and acceleration of a vibrating mass-spring system undergoing periodic motion. A motion sensor placed directly below a mass hung from a spring is used to record the vertical position of the mass for 1 second after the spring is stretched (beyond its resting point) and allowed to “spring back.” A computer program is used to analyze the data and plot displacement, velocity, and acceleration of the mass-spring system as a function of time (Figure 1).

Figure 1