14.1. Solve: The frequency generated by a guitar string is 440 Hz. The period is the inverse of the frequency,
= 2.27 103 s = 2.27 ms
f 440 Hz
14.2. Model: The air-track glider oscillating on a spring is in simple harmonic motion.
Model: A spinning skater, whose arms are outstretched, is a rigid rotating body.
Solve: The speed v = r , where r = 140 cm/2 = 0.70 m. Also, 180 rpm = (180)2 /60 rad/s = 6 rad/s. Thus,
v = (0.70 m)(6 rad/s) = 13.2 m/s.
Assess: A speed of
Model: Model the sun (s) and the earth (e) as spherical masses. Due to the large difference between
your size and mass and that of either the sun or the earth, a human body can be treated as a particle.
GM s M y
GM e M y
and Fe on you =
Solve: Fs on
11.1. Visualize: Please refer to Figure EX11.1.
Solve: (a) A B = AB cos = (4)(5)cos 40 = 15.3.
C D = CD cos = (2)(4)cos120 = 4.0.
E F = EF cos = (3)(4)cos90 = 0.
11.2. Visualize: Please refer to Figure EX11.2.
Solve: (a) A B = AB cos = (3)(4)cos11