25. A 7in. connecting rod in an engine connects the wrist pin of a piston at point A to the end of a second rod at point B on Page 718 the crankshaft. As the piston moves forward and back, the crankshaft is turned counterclockwise around point C. The stroke length of the engine is the distance that the piston travels (one way) within its cylinder. If the stroke length is 4 in., and the engine turns at 1800 rpm, write a model representing the distance d (in inches) from A to the center of the crank shaft C as a function of the time t (in minutes). Assume that at t = 0, the piston is at its farthest point from the crankshaft. 7 in. B A | : l | l B I | i | l | | | I H4 4 1n. stroke length I A \"mu-w\". I 35. The brightness of a \"young\" star sometimes increases and decreases as a result of regional areas of \"hot\" and \"cold\" on the star's surface as well as variations in the density of the star's planet-forming debris, which can obstruct light. Suppose that for a particular star, the average magnitude (measure of brightness) is 4.3 with a variation of 10.31 (on the magnitude scale, brighter Objects have a smaller magnitude than dimmer objects). Furthermore, the magnitude of a star is initially observed to be 4.61. and the time between minimum brightness and maximum brightness is 6.4 days. Write a simple harmonic motion model to describe the magnitude M of the star for day it