Questions and Answers
What is the constant force formula for work?
W = F * s * cos(θ)
What is a unit measure of work?
Define kinetic energy.
Kinetic energy is the energy possessed by an object due to its motion.
What does the work-energy theorem state?
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What is work done by the force of gravity?
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Define gravitational potential energy.
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What is the definition of gravitational potential energy?
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What is a conservative force?
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What is the relationship between mechanical energy and gravity?
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What does the principle of conservation of mechanical energy state?
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In a situation where the total mechanical energy is conserved, what happens to kinetic and potential energy?
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What conclusion can be reached if a net external nonconservative force does positive work on a particle?
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Which vehicle is obeying the principle of conservation of mechanical energy: a running sports car or a coasting truck?
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Study Notes
Work and Energy Concepts
- Work Constant Force Formula: Work (W) is defined as W = F * s * cos(θ), where F is force magnitude, s is displacement magnitude, and θ is the angle between force and displacement.
- Unit of Work: A newton meter (N·m) is the standard unit for measuring work.
Kinetic Energy
- Kinetic Energy (KE): Defined as the energy an object possesses due to its motion, often expressed as KE = 1/2 mv², where m is mass and v is velocity.
Work-Energy Theorem
- Work-Energy Theorem: States that the work done (W) on an object is equal to the change in its kinetic energy (KEf - KE0).
Gravitational Potential Energy
- Gravitational Potential Energy (PE): This is the energy held by an object based on its position above the Earth, expressed as PE = mgh, where m is mass, g is gravitational acceleration, and h is height.
Conservative Forces
- Definition of Conservative Force: A force is termed conservative if the work done is independent of the path taken; it only depends on the initial and final positions.
- Closed Path Condition: A conservative force does no net work when an object moves in a closed path, returning to its starting point.
Mechanical Energy
- Mechanical Energy: Defined as the sum of kinetic energy and potential energy (E = KE + PE).
- Conservation of Mechanical Energy: Mechanical energy remains constant in the absence of nonconservative forces (Wnc = 0 J).
Energy Dynamics
- Net Work and Energy Changes: The net work done by all forces relates directly to the changes in the object's kinetic and potential energy.
Problem Scenarios
- Fuel Tank Release Scenario: All tanks, regardless of initial speeds and directions, reach the same final speed upon hitting the ground due to conservation of energy principles.
- Mechanical Energy Conservation Test: If kinetic energy increases, potential energy must decrease, and vice versa, when mechanical energy is conserved.
Nonconservative Forces
- Positive Work by Nonconservative Forces: If a nonconservative force does positive work, the total mechanical energy of a particle increases.
Vehicle Energy Examples
- Sports Car vs. Truck on a Hill: The sports car does not obey conservation of mechanical energy because its engine adds energy, while the truck coasting up the hill abides by this principle, as no external energy is inputted.
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Description
This set of flashcards covers key concepts from Chapter 6 on Work and Energy. Learn definitions such as the work constant force formula, units of work, and the work-energy theorem. Perfect for mastering important physics principles related to work and energy.
