Textbook Question
A tennis racket swung over the server's head hits a tennis ball horizontally. Draw a free-body diagram for each object in the system. Use dashed lines to connect members of an action/reaction pair.
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Ch 07: Newton's Third Law
Knight Calc5th EditionPhysics for Scientists and EngineersISBN: 9780137344796
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Table of contents
- Ch 01: Concepts of Motion35
- Ch 02: Kinematics in One Dimension75
- Ch 03: Vectors and Coordinate Systems58
- Ch 04: Kinematics in Two Dimensions60
- Ch 05: Force and Motion23
- Ch 06: Dynamics I: Motion Along a Line53
- Ch 07: Newton's Third Law27
- Ch 08: Dynamics II: Motion in a Plane52
- Ch 09: Work and Kinetic Energy56
- Ch 10: Interactions and Potential Energy50
- Ch 11: Impulse and Momentum56
- Ch 12: Rotation of a Rigid Body71
- Ch 13: Newton's Theory of Gravity52
- Ch 14: Fluids and Elasticity44
- Ch 15: Oscillations55
- Ch 16: Traveling Waves37
- Ch 17: Superposition39
- Ch 18: A Macroscopic Description of Matter53
- Ch 19: Work, Heat, and the First Law of Thermodynamics60
- Ch 20: The Micro/Macro Connection53
- Ch 21: Heat Engines and Refrigerators34
- Ch 22: Electric Charges and Forces40
- Ch 23: The Electric Field39
- Ch 24: Gauss' Law32
- Ch 25: The Electric Potential63
- Ch 26: Potential and Field57
- Ch 27: Current and Resistance42
- Ch 28: Fundamentals of Circuits39
- Ch 29: The Magnetic Field47
- Ch 30: Electromagnetic Induction60
- Ch 31: Electromagnetic Fields and Waves32
- Ch 32: AC Circuits63
- Ch 33: Wave Optics32
- Ch 34: Ray Optics57
- Ch 35: Optical Instruments30
- Ch 36: Special Relativity38
- Ch 37: The Foundations of Modern Physics25
- Ch 38: Quantization49
- Ch 39: Wave Functions and Uncertainty31
- Ch 40: One-Dimensional Quantum Mechanics35
- Ch 41: Atomic Physics18
- Ch 42: Nuclear Physics27
Knight Calc5th EditionPhysics for Scientists and EngineersISBN: 9780137344796Not the one you use?Change textbook
Chapter 7, Problem 3a
A heavy steel cable attached to a motor is lifting a girder. The girder is speeding up. Draw an interaction diagram.
Verified step by step guidance1
Step 1: Identify the objects involved in the scenario. In this case, the objects are the steel cable, the motor, and the girder. These are the key components of the system interacting with each other.
Step 2: Determine the forces acting on the girder. The girder experiences the upward tension force exerted by the steel cable and the downward gravitational force due to its weight. Represent these forces clearly in the diagram.
Step 3: Consider the steel cable. The cable is under tension due to the motor pulling it upward and the girder's weight pulling it downward. Include these forces in the interaction diagram.
Step 4: Account for the motor's role. The motor applies a force to the steel cable, causing it to lift the girder. This force is responsible for the girder's acceleration. Represent this interaction in the diagram.
Step 5: Draw the interaction diagram. Use arrows to represent forces and label them appropriately (e.g., tension, weight). Indicate the direction of acceleration for the girder, showing that it is speeding up as it moves upward.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Free Body Diagram
A free body diagram (FBD) is a graphical representation used to visualize the forces acting on an object. In this context, it helps identify the forces acting on the girder as it is lifted, including tension from the cable and gravitational force. Understanding FBDs is crucial for analyzing the dynamics of the system and determining the net force acting on the girder.
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Free-Body Diagrams
Newton's Second Law of Motion
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, expressed as F = ma. This principle is essential for understanding why the girder is speeding up; the net force (tension minus weight) results in a positive acceleration. This law provides the foundation for analyzing the motion of the girder as it is lifted.
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Tension in a Cable
Tension is the force transmitted through a cable or rope when it is pulled tight by forces acting from opposite ends. In this scenario, the tension in the steel cable is responsible for lifting the girder against the force of gravity. Understanding how tension varies with the acceleration of the girder is key to accurately drawing the interaction diagram and analyzing the forces involved.
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Related Practice
Textbook Question
A weightlifter stands up at constant speed from a squatting position while holding a heavy barbell across his shoulders. Identify the "system" on your interaction diagram.
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Textbook Question
Block A in FIGURE EX7.4 is sliding down the incline. The rope is massless, and the massless pulley turns on frictionless bearings, but the surface is not frictionless. The rope and the pulley are among the interacting objects, but you'll have to decide if they're part of the system. Draw an interaction diagram.
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Textbook Question
How much force does the astronaut exert on his chair while accelerating straight up at 10 m/s2?
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Textbook Question
Block A in FIGURE EX7.4 is sliding down the incline. The rope is massless, and the massless pulley turns on frictionless bearings, but the surface is not frictionless. The rope and the pulley are among the interacting objects, but you'll have to decide if they're part of the system. Draw a free-body diagram for each object in the system. Use dashed lines to connect members of an action/reaction pair.
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