A 20-m long steel wire (cross-section 1.0 cm2, Young's modulus 2.0 1011 N/m2), is subjected to a load of 25 000 N. How much will the wire stretch under the load?
a. 0.25 cm
b. 2.5 cm
c. 12.5 cm
d. 25 cm
e. 1.25 cm
[Ques. 2] A horizontal uniform meter stick supported at the 50-cm mark has a mass of 0.50 kg hanging from it at the 20-cm mark and a 0.30-kg mass hanging from it at the 60-cm mark. Determine the position on the meter stick at which one would hang a third mass of 0.60 kg to keep the meter stick balanced.
a. 74 cm
b. 70 cm
c. 65 cm
d. 86 cm
e. 62 cm
[Ques. 3] A uniform ladder 15 ft long is leaning against a frictionless wall at an angle of 53 above the horizontal. The weight of the ladder is 30 pounds. A 75-lb boy climbs 6.0-ft up the ladder. What is the magnitude of the friction force exerted on the ladder by the floor?
a. 43 lb
b. 34 lb
c. 38 lb
d. 47 lb
e. 24 lb
[Ques. 4] A wheel (radius = 12 cm) is mounted on a frictionless, horizontal axle that is perpendicular to the wheel and passes through the center of mass of the wheel. A light cord wrapped around the wheel supports a 0.40-kg object. If released from rest with the string taut, the object is observed to fall with a downward acceleration of 3.0 m/s2 . What is the rotational inertia (of the wheel) about the given axle?
a. 0.023 kg/m2
b. 0.013 kg/m2
c. 0.020 kg/m2
d. 0.016 kg/m2
e. 0.035 kg/m2
[Ques. 5] Three particles, each of which has a mass of 80 g, are positioned at the vertices of an equilateral triangle with sides of length 60 cm. The particles are connected by rods of negligible mass. What is the moment of inertia of this rigid body about an axis that is parallel to one side of the triangle and passes through the respective midpoints of the other two sides?
a. 0.018 kg/m2
b. 0.020 kg/m2
c. 0.016 kg/m2
d. 0.022 kg/m2
e. 0.032 kg/m2
[Ques. 6] Four identical particles (mass of each = 0.40 kg) are placed at the vertices of a rectangle (2.0 m 3.0 m) and held in those positions by four light rods which form the sides of the rectangle. What is the rotational inertia of this rigid body about an axis that passes through the mid-points of the longer sides and is parallel to the shorter sides?
a. 2.7 kg/m2
b. 3.6 kg/m2
c. 3.1 kg/m2
d. 4.1 kg/m2
e. 1.6 kg/m2
[Ques. 7] Four identical particles (mass of each = 0.40 kg) are placed at the vertices of a rectangle (2.5 m 4.0 m) and held in those positions by four light rods which form the sides of the rectangle. What is the rotational inertia of this rigid body about an axis that passes through the mid-points of the shorter sides and is parallel to the longer sides?
a. 2.2 kg/m2
b. 2.8 kg/m2
c. 2.5 kg/m2
d. 3.1 kg/m2
e. 1.6 kg/m2
[Ques. 8] Four identical particles (mass of each = 0.24 kg) are placed at the vertices of a rectangle (2.0 m 3.0 m) and held in those positions by four light rods which form the sides of the rectangle. What is the rotational inertia of this rigid body about an axis that passes through the center of mass of the body and is parallel to the shorter sides of the rectangle?
a. 2.4 kg/m2
b. 2.2 kg/m2
c. 1.9 kg/m2
d. 2.7 kg/m2
e. 8.6 kg/m2
[Ques. 9] Two particles (m1 = 0.20 kg, m2 = 0.30 kg) are positioned at the ends of a 2.0-m long rod of negligible mass. What is the rotational inertia of this rigid body about an axis perpendicular to the rod and through the center of mass?
a. 0.48 kg/m2
b. 0.50 kg/m2
c. 1.2 kg/m2
d. 0.80 kg/m2
e. 0.70 kg/m2
[Ques. 10] What is the angular momentum of the Moon about the Earth? The mass of the Moon is 7.35 1022 kg, the center-to-center separation of the Earth and the Moon is 3.84 105 km, and the orbital period of the Moon is 27.3 days. Ignore the small offset of the center of mass of the system from the center of the Earth in your calculation.
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