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Work and Energy flashcards
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- What is work by a constant force?Work
- W = Fd cosθ.
- What is the work unit?Work
- Joule, equal to N·m.
- When is work negative?Work
- When a force has a component opposite displacement.
- When is work zero?Work
- When force is perpendicular to displacement or displacement is zero.
- What is work in mechanics?Work
- Energy transfer associated with force along displacement.
- When is a force’s work zero?Work
- When force is perpendicular to displacement, or displacement is zero.
- What is power?Work
- Rate of energy transfer.
- What does net work change?Work
- Kinetic energy.
- What is translational kinetic energy?Kinetic and Potential Energy
- K = 1/2 mv².
- Does kinetic energy have a direction?Kinetic and Potential Energy
- No, it is a scalar.
- What happens to K if speed doubles?Kinetic and Potential Energy
- It becomes four times as large at fixed mass.
- What happens to K if mass doubles?Kinetic and Potential Energy
- It doubles at fixed speed.
- What is kinetic energy?Kinetic and Potential Energy
- Energy associated with motion in the chosen frame.
- How does doubling speed affect K at fixed mass?Kinetic and Potential Energy
- It multiplies K by four.
- What sets zero gravitational potential energy?Kinetic and Potential Energy
- A chosen reference.
- When is ½kx² appropriate?Kinetic and Potential Energy
- For a linear spring in its elastic range.
- What is mechanical energy?Conservation of Energy
- A sum of selected kinetic and potential energies.
- When is E_mech approximately constant?Conservation of Energy
- When external work and nonconservative transfers are negligible.
- What happens to U_g during a fall?Conservation of Energy
- It decreases as height decreases.
- Where can lost mechanical energy go?Conservation of Energy
- To thermal or other energy stores in surroundings.
- What is efficiency?Conservation of Energy
- Useful output energy divided by input energy.
- Why specify an energy system?Conservation of Energy
- To identify storage and transfers across its boundary.