## College Physics Reasoning and Relationships

Physics & Astronomy

## Quiz 8 :

Rotational Motion

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Q01 Q01 Q01

Two points on a merry-go-round are located at distances from the center r

_{1}and r_{2}, where r_{1}< r_{2}. While the merry-go-round is in the process of speeding up to operational speed, which of the following equations involving magnitudes of angular speed, angular acceleration, and linear speed for these points is incorrect?Free

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B

Q06 Q06 Q06

A ceiling fan is turned on and reaches an angular speed of 120 rev/min in 20 s. It is then turned off and coasts to a stop in an additional 60 s. The ratio of the average angular acceleration for the first 20 s to that for the last 60 s is which of the following?

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Q14 Q14 Q14

Suppose a car has a 100,000 mile 10 year warranty on the wheels and axles of a car. How may turns will the wheels of 0.80-m diameter make if both the mileage and time warranties run out simultaneously and what will be the average angular velocities of the wheel? Assume that a mile = m and that a year is s.

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Q16 Q16 Q16

A circular disk is rotating about a central axis with an angular velocity which is increasing at a constant rate. Point 1 on the disk is located at a distance from the center of the disk and point 2 on the disk is located at a distance from the center of the disk. If , which of the following ratios is the largest? 1 and 2 refer to being at points 1 and 2 in the subscripts below, all values occurring at the same time.

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Q17 Q17 Q17

The torque caused by a force F applied at a distance r from the axis of rotation, is given by , where is the angle between and . If the magnitudes r and F remain the same, what other angle will produce the same torque as was produced at angle if was less than 90°?

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Q19 Q19 Q19

Two equal magnitude forces are in opposite directions, and their lines of action are separated by distance d. These two forces are applied to a solid disk, which is mounted on a frictionless axle. If d is half the radius r of the disk, which of the following positions for the forces would give the most torque?

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Q20 Q20 Q20

A 3.0-m rod is pivoted about its left end. A force of 10 N is applied perpendicular to the rod at a distance of 1.2 m from the pivot causing a ccw torque, and a force of 5.2 N is applied at the end of the rod 3.0 m from the pivot. The 5.2-N force is at an angle of 30

^{o}to the rod and causes a cw torque. What is the net torque about the pivot? (Take ccw as positive.)Free

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Q21 Q21 Q21

A rod of length L is pivoted about its left end and has a force F applied perpendicular to the other end. The force F is now removed and another force F is applied at the midpoint of the rod. If F is at an angle of 30

^{o}with respect to the rod, what is its magnitude if the resulting torque is the same as when F was applied?Free

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Q23 Q23 Q23

Two children seat themselves on a seesaw. The one on the left has a weight of 400 N while the one on the right weighs 300 N. The fulcrum is at the midpoint of the seesaw. If the child on the right is not at the end but is 1.50 m from the fulcrum and the seesaw is balanced, what is the torque provided by the weight of the child on the left? (Take ccw as positive.)

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Q24 Q24 Q24

A bucket filled with water has a mass of 23 kg and is attached to a rope, which in turn, is wound around a 0.080-m radius cylinder at the top of a well. What torque does the weight of water and bucket produce on the cylinder if the cylinder is not permitted to rotate? (g = 9.8 m/s

^{2})Free

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Q25 Q25 Q25

A bucket of water with total mass 23 kg is attached to a rope, which in turn, is wound around a 0.080-m radius cylinder at the top of a well. A crank with a turning radius of 0.25 m is attached to the end of the cylinder. What minimum force directed perpendicular to the crank handle is required to just raise the bucket? (Assume the rope's mass is negligible, that the cylinder turns on frictionless bearings, and that g = 9.8 m/s

^{2}.)Free

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Q27 Q27 Q27

Tasha has mass 20 kg and wants to use a 6.0-m board of mass 10 kg as a seesaw. Her friends are busy, so Tasha seesaws by herself by putting the support at the system's center of gravity when she sits on one end of the board. How far is she from the support point?

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Q34 Q34 Q34

A uniform, horizontal beam of length 6.0 m and weight 140 N is attached at one end to a wall by a pin connection (so that it may rotate). A cable attached to the wall above the pin supports the opposite end. The cable makes an angle of 60 with the horizontal. What is the tension in the cable needed to maintain the beam in equilibrium?

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Q35 Q35 Q35

A uniform 1.0-N meterstick is suspended horizontally by vertical strings attached at each end. A 2.0-N weight is suspended from the 10-cm position on the stick, another 2.0-N weight is suspended from the 50-cm position, and a 3.0-N weight is suspended from the 60-cm position. What is the tension in the string attached at the 100-cm end of the stick?

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Q36 Q36 Q36

A uniform rod of length L and weight W is placed on a fulcrum a distance of 0.4L from the left end. On the left end is placed a mass of weight 2W and on the right end a vertical force F is applied to keep the system in balance. What are the magnitude and direction of the force F?

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Q45 Q45 Q45

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 at the top of a well. The bucket is raised to the top of the well and released. The bucket is moving with a speed of 6.0 m/s upon hitting the water surface in the well. What is the angular speed of the cylinder at this instant?

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Q46 Q46 Q46

A majorette takes two batons and fastens them together in the middle at right angles to make an "x" shape. Each baton was 0.90 m long and each ball on the end is 0.20 kg. (Ignore the mass of the rods.) What is the moment of inertia if the arrangement is spun around an axis formed by one of the batons?

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Q47 Q47 Q47

A majorette takes two batons and fastens them together in the middle at right angles to make an "x" shape. Each baton was 0.90 m long and each ball on the end is 0.20 kg. (Ignore the mass of the rods.) What is the moment of inertia if the arrangement is spun around an axis through the center perpendicular to both rods?

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Q48 Q48 Q48

Two hoops or rings (I = MR

^{2}) are centered, lying on a turntable. The smaller ring has radius = 0.050 m; the larger has radius = 0.10 m. Both have a mass of 6.0 kg. What is the total moment of inertia as the turntable spins? Ignore the mass of the turntable.Free

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Q49 Q49 Q49

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 end masses:

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Q51 Q51 Q51

A non-uniform rod of length L and mass M is pivoted about one end. The moment of inertia of this rod about its pivoted end is . Attached to the rod is a mass M at its midpoint and at the end opposite the pivot is another mass 2M. What is the moment of inertia of this configuration about the pivot?

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Q69 Q69 Q69

A baseball pitcher, loosening up his arm before a game, tosses a 0.15-kg ball using only the rotation of his forearm, 0.32 m in length, to accelerate the ball. If the ball starts at rest and is released with a speed of 24 m/s in a time of 0.40 s, what is the average angular acceleration of the arm and ball?

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Q70 Q70 Q70

A baseball pitcher loosens up his pitching arm. He tosses a 0.15-kg ball using only the rotation of his forearm, 0.32 m in length, to accelerate the ball. If the ball starts at rest and is released with a speed of 24 m/s in a time of 0.40 s, what torque is applied to the ball while being held by the pitcher's hand to produce the angular acceleration?

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Q71 Q71 Q71

A bucket of water with total mass 30 kg is attached to a rope, which in turn is wound around a 0.050 m radius cylinder at the top of a well. A crank with a turning radius of 0.25 m is attached to the end of the cylinder and the moment of inertia of cylinder and crank is 0.12 kgm

^{2}. If the bucket is raised to the top of the well and released, what is the acceleration of the bucket as it falls toward the bottom of the well? (Assume rope's mass is negligible, that cylinder turns on frictionless bearings and that g = 9.8 m/s^{2}.)Free

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Q73 Q73 Q73

A rod of length L is hinged at one end. The moment of inertia as the rod rotates around that hinge is ML

^{2}/3. Suppose a 2.50 m rod with a mass of 3.00 kg is hinged at one end and is held in a horizontal position. The rod is released as the free end is allowed to fall. What is the angular acceleration as it is released?Free

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