Download prob left physics hw 3

3. [HRW8 9.P.046.] --/1 points Saved Work | View Last Response | Show Details
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In the figure, a stationary block explodes into two pieces L and R that slide across a
frictionless floor and then into regions with friction, where they stop. Piece L, with a
mass of 2.2 kg, encounters a coefficient of kinetic friction µL = 0.40 and slides to a stop
in distance dL = 0.15 m. Piece R encounters a coefficient of kinetic friction µR = 0.50 and
slides to a stop in distance dR = 0.30 m. What was the mass of the original block?
1.39140219
kg
Section 9-7
10. [HRW8 10.P.071.] 0/1 points Last Response | View Saved Work | Show Details
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In the figure below, a small disk of radius r = 2.00 cm has been glued to the edge of a
larger disk of radius R = 4.00 cm so that the disks lie in the same plane. The disks can be
rotated around a perpendicular axis through point O at the center of the larger disk. The
disks both have a uniform density (mass per unit volume) of 1.10 103 kg/m3 and a
uniform thickness of 4.50 mm. What is the rotational inertia of the two-disk assembly
about the rotation axis through O?
3.52
kg·m2
Density is the ratio of mass to volume. The rotational inertia of a disk about its central
axis is given in Table 10-2. The rotational inertia about an axis shifted from the central
axis is given by the parallel-axis theorem.
14. [HRW8 12.P.028.] --/3 points Saved Work | Show Details
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In the figure below, a 48.0 kg uniform square sign, of edge L = 2.00 m, is hung from a
horizontal rod of length dh = 3.00 m and negligible mass. A cable is attached to the end of
the rod and to a point on the wall at distance dv = 4.00 m above the point where the rod is
hinged to the wall.
(a) What is the tension in the cable?
N
(b) What are the magnitude and direction of the horizontal component of the force on the
rod from the wall? (Include the sign. Take the positive direction to be to the right.)
N
(c) What are the magnitude and direction of the vertical component of this force?
(Include the sign. Take the positive direction to be upward.)
N
Did you write A balance-of-torques equation, using the hinge as the rotation axis for
calculating torques? Did you apply the force due to the sign's weight midway between the
sign's attachment points? Do you recall how to calculate a torque given a force's
magnitude and angle? After you get the tension, did you apply A balance-of-forces
equation horizontally and vertically?
Section 12-5
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A uniform beam is 5.0 m long and has a mass of 56 kg. In the figure below, the beam is
supported in a horizontal position by a hinge and a cable, with angle θ = 50°. In unitvector notation, what is the force on the beam from the hinge?
hinge
=(
N) + (
N)
Did you write A balance-of-torques equation, using the hinge as the rotation axis about
which to calculate torques? (Did you recall how to calculate a torque from a force's
magnitude and direction?) Did you write A balance-of-forces equation for vertical force
components? For horizontal force components?
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