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.
Discuss the differences between the Biot-Savart law and Coulomb’s law in terms of their applicationsand the physical quantities they describe.
Explain why Ampere’s law can be used to find the magnetic field inside a solenoid but not outside.
3. An Atwood machine consists of two masses, mA
and m B, which are connected by an inelastic cord
of negligible mass that passes over a pulley. If the
pulley has radius RO and
moment of inertia I about its axle, determine the
acceleration of the masses
mA and m B, and compare to the situation where the
moment of inertia of the
pulley is ignored. Ignore friction at the axle O. Use
angular momentum and torque in this solution
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