(II) The human leg can be compared to a physical pendulum, with a “natural” swinging period al which walking is easiest. Consider the leg as two rods joined rigidly together at the knee; the axis for the leg is the hip joint. The length of each rod is about the same, 55 cm. The upper rod has a mass of 7.0 kg and the lower rod has a mass of 4.0 kg. ( a ) Calculate the natural swinging period of the system. ( b ) Check your answer by standing on a chair and measuring the time for one or more complete back-and-forth swings. The effect of a shorter leg is a shorter swinging period, enabling a faster “natural” stride.
(II) The human leg can be compared to a physical pendulum, with a “natural” swinging period al which walking is easiest. Consider the leg as two rods joined rigidly together at the knee; the axis for the leg is the hip joint. The length of each rod is about the same, 55 cm. The upper rod has a mass of 7.0 kg and the lower rod has a mass of 4.0 kg. ( a ) Calculate the natural swinging period of the system. ( b ) Check your answer by standing on a chair and measuring the time for one or more complete back-and-forth swings. The effect of a shorter leg is a shorter swinging period, enabling a faster “natural” stride.
(II) The human leg can be compared to a physical pendulum, with a “natural” swinging period al which walking is easiest. Consider the leg as two rods joined rigidly together at the knee; the axis for the leg is the hip joint. The length of each rod is about the same, 55 cm. The upper rod has a mass of 7.0 kg and the lower rod has a mass of 4.0 kg. (a) Calculate the natural swinging period of the system. (b) Check your answer by standing on a chair and measuring the time for one or more complete back-and-forth swings. The effect of a shorter leg is a shorter swinging period, enabling a faster “natural” stride.
(II) A potter’s wheel is rotating around a vertical axis through its center at a frequency of 1.5 rev/s. The wheel can be considered a uniform disk of mass 5.0 kg and diameter 0.40 m. The potter then throws a 2.6-kg chunk of clay,approximately shaped as a flat disk of radius 7.0 cm, onto the center of the rotating wheel. What is the frequency of the wheel after the clay sticks to it? Ignore friction.
(3) The 12-lb lever OA with 10-in. radius of
gyration about point O is initially at rest in
the vertical position (0 = 90°), where the
attached spring of stiffness k= 3 lb/in is
unstretched. Calculate the constant moment
M applied to the lever at O which will give
the lever an angular velocity o = 4 rad/sec
as the lever rotates to the horizontal position
at 0 = 0.
k = 3 lb/in.
ww
15"
15"
(c) A small ball of mass 0.75 kg is attached to one end of a 1.25 m long
massless rod, and the other end of the rod is hung from a pivot.
When the resulting pendulum is 30° from the vertical, what is the
magnitude of the gravitational torque calculated about the pivot?
Chapter 14 Solutions
Physics for Scientists and Engineers with Modern Physics
Sears And Zemansky's University Physics With Modern Physics
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