Work, Energy, and Machines flashcards

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What is kinetic energy?Energy Forms and Transfers: Energy associated with motion.
What is gravitational potential energy?Energy Forms and Transfers: Energy associated with position in a gravitational interaction.
What is thermal energy?Energy Forms and Transfers: Energy associated with microscopic particle motion and interactions.
What is the SI energy unit?Energy Forms and Transfers: Joule (J).
What is work as energy transfer?Energy Forms and Transfers: Energy transfer by a force acting through displacement.
What is heating?Energy Forms and Transfers: Energy transfer due to a temperature difference.
Can radiation cross a vacuum?Energy Forms and Transfers: Yes.
Is heat a substance stored in an object?Energy Forms and Transfers: No; heat refers to a transfer process.
What is useful efficiency?Energy Forms and Transfers: Useful energy output divided by total input.
What is a Sankey diagram?Energy Forms and Transfers: A flow diagram showing energy input and output paths.
What happens to non-useful energy?Energy Forms and Transfers: It transfers to other stores or surroundings.
Can device efficiency vary?Energy Forms and Transfers: Yes, with conditions and load.
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 near-Earth ΔU_g?Kinetic and Potential Energy: mgΔh.
What does Δh represent?Kinetic and Potential Energy: Final height minus initial height.
Does ramp path length set gravitational ΔU?Kinetic and Potential Energy: No; vertical height change does.
What system has gravitational potential energy?Kinetic and Potential Energy: The interacting object–Earth system.
What is Hooke’s law magnitude?Kinetic and Potential Energy: F = k|x| in a linear elastic range.
What is ideal spring potential energy?Kinetic and Potential Energy: U_s = 1/2 kx².
What is k?Kinetic and Potential Energy: Spring constant, measured in N/m.
When does the simple spring model fail?Kinetic and Potential Energy: Outside its approximately linear 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 does friction often do to mechanical energy?Conservation of Energy: Transfers it to internal energy and other outputs.
What sign is friction work during sliding?Conservation of Energy: Usually negative for the sliding object.
What is internal energy?Conservation of Energy: Energy associated with microscopic states of a system.
Why state a system boundary?Conservation of Energy: To classify transfers versus internal changes.
Can a subsystem gain energy?Conservation of Energy: Yes, through transfer across its boundary.
What is an isolated idealized system?Conservation of Energy: One exchanging neither matter nor energy.
What is a closed system in common use?Conservation of Energy: One with no matter exchange, though energy may cross.
What does a complete account compare?Conservation of Energy: Initial and final stores plus boundary transfers.
What is work by a constant force?Work and Power: W = Fd cosθ.
What is the work unit?Work and Power: Joule, equal to N·m.
When is work negative?Work and Power: When a force has a component opposite displacement.
When is work zero?Work and Power: When force is perpendicular to displacement or displacement is zero.
What is average power?Work and Power: Energy transferred divided by elapsed time.
What is one watt?Work and Power: One joule per second.
What is the power formula?Work and Power: P = ΔE/Δt.
Can equal energy imply different power?Work and Power: Yes, when transfer times differ.
What is the work–energy theorem?Work and Power: W_net = ΔK.
What does positive net work imply?Work and Power: Translational kinetic energy increases.
What does negative net work imply?Work and Power: Translational kinetic energy decreases.
Does only applied-force work equal ΔK?Work and Power: Not if other forces do work.
What is mechanical advantage?Simple Machines and Efficiency: Output force divided by input force in a specified setup.
What is ideal work balance?Simple Machines and Efficiency: F_in d_in = F_out d_out.
Does a simple machine create energy?Simple Machines and Efficiency: No.
Why can real output work be less?Simple Machines and Efficiency: Friction and other transfers reduce useful output.
What is a fulcrum?Simple Machines and Efficiency: The pivot point of a lever.
What is a lever arm?Simple Machines and Efficiency: Distance from pivot to a force’s line of action in the simple model.
What does an incline trade?Simple Machines and Efficiency: Longer path for smaller required along-slope force.
What does a fixed pulley mainly change ideally?Simple Machines and Efficiency: Direction of the applied force.
What is machine efficiency?Simple Machines and Efficiency: Useful output energy divided by input energy, times 100%.
How is mechanical advantage different?Simple Machines and Efficiency: It is a force ratio, not an energy fraction.
What is an ideal machine?Simple Machines and Efficiency: A model with no non-useful transfers.
What should a short-interval account include?Simple Machines and Efficiency: Changes in temporarily stored energy.