ornament's center. If the ornament has mass 0.0074 kg and radius 0.036 m, what is its moment of inertia for an axis that
passes through its center?
kg·m^24.3 Three glass panels, each 2.7 m tall and 1.6 m
wide and with mass 23 kg, are joined together
to make a rotating door. The axis of rotation is
the line where the panels join together. A
person pushes perpendicular to a panel at its
outer edge with a force of 73 N. What is the
angular acceleration of the door?rad/s^24.4 A solid cylinder 0.230 m long and with a radius
of 0.0730 m is rotated around an axis through
its middle and parallel to its ends, as shown. A
constant net torque of 1.20 N·m is applied to
the cylinder, resulting in an angular
acceleration of 23.0 rad/s^2. What is the mass
of the cylinder?
kg
4.5 Two golf balls are glued together and rotated about an axis through the point where they are joined. The axis is tangent to
both golf balls. The mass of a golf ball is 0.046 kg and its radius is 0.021 m. What is the moment of inertia of the pair of golf
balls around the chosen axis?
kg·m^24.6 Bob and Ray push an ordinary door from opposite sides. Both of them push perpendicular to the door. Bob pushes 0.670 m
from the hinge with a force of 121 N. Ray pushes 0.582 m from the hinge with force of 132 N. Consider the door as a slab,
with height 2.03 m, width 0.813 m, and mass 13.6 kg. What is the magnitude of the angular acceleration of the door?
rad/s^2
4.7 A potter's wheel consists of a uniform concrete disk, 0.035 m thick and with a radius of 0.42 m. It has a mass of 48 kg. The
wheel is rotating freely with an angular velocity of 9.6 rad/s when the potter stops it by pressing a wood block against the edge
of the wheel, directing a force of 65 N on a line toward the center of the wheel. If the wheel stops in 7.2 seconds, what is the
coefficient of friction between the block and the wheel?4.8 Two thin, square slabs of metal, each with side length of 0.30 m and mass 0.29 kg, are welded together in a T shape and
rotated on an axis through their line of intersection. What is the moment of inertia of the T?
kg·m^2
Section 6 - Interactive problem: close the bridge
6.1 Use the simulation in the interactive problem in this section to answer the following question. What is the force required to
close the bridge with the desired angular acceleration? Test your answer using the simulation.
NSection 8 - Angular momentum of a particle in circular motion
8.1 What is the magnitude of angular momentum of a 1070 kg car going around a circular curve with a 15.0 m radius at
12.0 m/s? Assume the origin is at the center of the curve's arc.
kg·m^2 /s
8.2 Calculate the magnitude of the angular momentum of the Earth around the Sun, using the Sun as the origin. The Earth's
mass is 5.97×10^24 kg and its roughly circular orbit has a radius of 1.50×10^11 m. Use a 365-day year with exactly 24 hours in
each day.
kg·m^2 /s