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Ch 10: Dynamics of Rotational Motion
Young & Freedman Calc - University Physics 14th Edition
Young & Freedman Calc14th EditionUniversity PhysicsISBN: 9780321973610Not the one you use?Change textbook
Chapter 10, Problem 13a

A 2.00-kg textbook rests on a frictionless, horizontal surface. A cord attached to the book passes over a pulley whose diameter is 0.150 m, to a hanging book with mass 3.00 kg. The system is released from rest, and the books are observed to move 1.20 m in 0.800 s. What is the tension in each part of the cord?

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1
Start by identifying the forces acting on each book. The 2.00-kg textbook on the frictionless surface experiences tension from the cord, while the 3.00-kg hanging book experiences both tension and gravitational force.
Use Newton's second law to set up equations for each book. For the 2.00-kg book, the equation is: \( T_1 = m_1 \cdot a \), where \( T_1 \) is the tension in the cord attached to the 2.00-kg book, \( m_1 = 2.00 \) kg, and \( a \) is the acceleration.
For the 3.00-kg hanging book, the equation is: \( m_2 \cdot g - T_2 = m_2 \cdot a \), where \( T_2 \) is the tension in the cord attached to the 3.00-kg book, \( m_2 = 3.00 \) kg, and \( g \) is the acceleration due to gravity (approximately 9.81 m/s²).
Calculate the acceleration \( a \) using the kinematic equation: \( s = \frac{1}{2} a t^2 \), where \( s = 1.20 \) m is the distance moved, and \( t = 0.800 \) s is the time taken. Rearrange to solve for \( a \).
Substitute the calculated acceleration \( a \) into the equations for \( T_1 \) and \( T_2 \) to find the tension in each part of the cord. Ensure to keep the units consistent throughout the calculations.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Newton's Second Law

Newton's Second Law states that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass (F = ma). In this problem, it helps determine the acceleration of the system by considering the forces acting on both the textbook and the hanging book.
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Kinematics

Kinematics involves the study of motion without considering the forces that cause it. Using the kinematic equations, we can calculate the acceleration of the books based on their displacement and time. This is crucial for understanding how the system evolves from rest to moving 1.20 m in 0.800 s.
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Tension in a Cord

Tension refers to the force transmitted through a string, rope, or cord when it is pulled tight by forces acting at each end. In this scenario, the tension in the cord is affected by the masses of the books and their acceleration. Calculating tension involves analyzing the forces in the system, including gravitational force on the hanging book.
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Related Practice
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A 2.20-kg hoop 1.20 m in diameter is rolling to the right without slipping on a horizontal floor at a steady 2.60 rad/s. Find the velocity vector of each of the following points, as viewed by a person at rest on the ground: (i) the highest point on the hoop; (ii) the lowest point on the hoop; (iii) a point on the right side of the hoop, midway between the top and the bottom.

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Textbook Question

A machine part has the shape of a solid uniform sphere of mass 225 g and diameter 3.00 cm. It is spinning about a frictionless axle through its center, but at one point on its equator it is scraping against metal, resulting in a friction force of 0.0200 N at that point. How long will it take to decrease its rotational speed by 22.5 rad/s?

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Textbook Question

A stone is suspended from the free end of a wire that is wrapped around the outer rim of a pulley, similar to what is shown in Fig. 10.10. The pulley is a uniform disk with mass 10.0 kg and radius 30.0 cm and turns on frictionless bearings. You measure that the stone travels 12.6 m in the first 3.00 s starting from rest. Find the tension in the wire.

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Textbook Question

A stone is suspended from the free end of a wire that is wrapped around the outer rim of a pulley, similar to what is shown in Fig. 10.10. The pulley is a uniform disk with mass 10.0 kg and radius 30.0 cm and turns on frictionless bearings. You measure that the stone travels 12.6 m in the first 3.00 s starting from rest. Find the mass of the stone.

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Textbook Question

A 15.0-kg bucket of water is suspended by a very light rope wrapped around a solid uniform cylinder 0.300 m in diameter with mass 12.0 kg. The cylinder pivots on a frictionless axle through its center. The bucket is released from rest at the top of a well and falls 10.0 m to the water. With what speed does the bucket strike the water?

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Textbook Question

A 12.0-kg box resting on a horizontal, frictionless surface is attached to a 5.00-kg weight by a thin, light wire that passes over a frictionless pulley (Fig. E10.16). The pulley has the shape of a uniform solid disk of mass 2.00 kg and diameter 0.500 m. After the system is released, find the acceleration of the box.

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