An approximate model for a ceiling fan consists of a cylindrical disk with four thin rods extending from the disk’s center, as in Figure P8.41. The disk has mass 2.50 kg and radius 0.200 m. Each rod has mass 0.850 kg and is 0.750 m long, (a) Find the ceiling fan’s moment of inertia about a vertical axis through the disk’s center, (b) Friction exerts a constant torque of magnitude 0.115 N · m on the fan as it rotates. Find the magnitude of the constant torque provided by the fan’s motor if the fan starts from rest and takes 15.0 s and 18.5 full revolutions to reach its maximum speed. Figure P8.41
An approximate model for a ceiling fan consists of a cylindrical disk with four thin rods extending from the disk’s center, as in Figure P8.41. The disk has mass 2.50 kg and radius 0.200 m. Each rod has mass 0.850 kg and is 0.750 m long, (a) Find the ceiling fan’s moment of inertia about a vertical axis through the disk’s center, (b) Friction exerts a constant torque of magnitude 0.115 N · m on the fan as it rotates. Find the magnitude of the constant torque provided by the fan’s motor if the fan starts from rest and takes 15.0 s and 18.5 full revolutions to reach its maximum speed. Figure P8.41
Solution Summary: The author explains the ceiling fan's moment of inertia about vertical axis through the disk’s center.
An approximate model for a ceiling fan consists of a cylindrical disk with four thin rods extending from the disk’s center, as in Figure P8.41. The disk has mass 2.50 kg and radius 0.200 m. Each rod has mass 0.850 kg and is 0.750 m long, (a) Find the ceiling fan’s moment of inertia about a vertical axis through the disk’s center, (b) Friction exerts a constant torque of magnitude 0.115 N · m on the fan as it rotates. Find the magnitude of the constant torque provided by the fan’s motor if the fan starts from rest and takes 15.0 s and 18.5 full revolutions to reach its maximum speed.
A pendulum has a 0.4-m-long cord and is given a tangential velocity of 0.2 m/s toward the
vertical from a position 0 = 0.3 rad.
Part A
Determine the equation which describes the angular motion.
Express your answer in terms of the variable t. Express coefficients in radians to three significant figures.
ΜΕ ΑΣΦ
vec
(t)=0.3 cos (4.95t) + 0.101 sin (4.95t)
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Part A
■Review
The uniform 150-lb stone (rectangular block) is being turned over on its side by pulling the
vertical cable slowly upward until the stone begins to tip.
(Figure 1)
If it then falls freely (T = 0) from an essentially balanced at-rest position, determine the speed at which the corner A strikes the pad at B. The stone does not slip at its corner C as it falls. Suppose that height of the stone is
L = 1.2 ft.
Express your answer to three significant figures and include the appropriate units.
?
ft
VA 10.76
S
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Consider the circuit shown in the figure. The battery has emf ε = 69 volts and negligible internal resistance. The inductance is L = 0.4 H and the resistances are R 1 = 12 Ω and R 2 = 9.0 Ω. Initially the switch S is open and no currents flow. Then the switch is closed. After leaving the switch closed for a very long time, it is opened again. Just after it is opened, what is the current in R 1?
Chapter 8 Solutions
Bundle: College Physics, Loose-Leaf Version, 11th + WebAssign Printed Access Card for Serway/Vuille's College Physics, 11th Edition, Multi-Term
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