46. An object consists of a rod (of length 3.0 : 2102159
46. An object consists of a rod (of length 3.0 m and negligible moment of inertia) to which four small 2.0-kg masses are attached, one at each end and one at each point on the rod 1.0 m from each end. (The masses are one meter apart.) The moment of inertia of this object about an axis perpendicular to the rod and through one of the inner masses:
A. is 72 kg?m2.
B. is 12 kg?m2.
C. is 4 kg?m2.
D. cannot be uniquely determined until it is stated which inner mass the axis goes through.
47. A ventilation fan with a moment of inertia of 0.034 kg?m2 has a net torque of 0.11 N?m applied to it. If it starts from rest, what kinetic energy will it have 8.0 s later?
A. 31 J
B. 17 J
C. 11 J
D. 6.6 J
48. The total kinetic energy of a baseball thrown with a spinning motion is a function of:
A. its linear speed but not rotational speed.
B. its rotational speed but not linear speed.
C. both linear and rotational speeds.
D. neither linear nor rotational speed.
49. A bowling ball has a mass of 7.0 kg, a moment of inertia of 2.8 ´ 10-2 kg?m2 and a radius of 0.10 m. If it rolls down the lane without slipping at a linear speed of 4.0 m/s, what is its total kinetic energy?
A. 45 J
B. 32 J
C. 11 J
D. 78 J
50. A bucket of water with total mass 23 kg is attached to a rope, which in turn is wound around a 0.050-m radius cylinder, with crank, at the top of a well. The moment of inertia of the cylinder and crank is 0.12 kg?m2. The bucket is raised to the top of the well and released to fall back into the well. What is the kinetic energy of the cylinder and crank at the instant the bucket is moving with a speed of 8.0 m/s?
A. 2.1 ´ 103 J
B. 1.5 ´ 103 J
C. 0.70 ´ 103 J
D. 0.40 ´ 103 J