Chapter 3 Energy Vocabulary Flashcards

Vocabulary flashcards covering key terms from Chapter 3 on energy, work, power, momentum, and relativity.

Work

A measure of the change produced by a force; W = F × d; requires motion in the direction of the force; unit is the joule (N·m).

Force

The physical cause of motion and changes in motion; defined by Newton’s second law: F = m × a.

Energy

The ability to do work.

Kinetic Energy (KE)

Energy of motion; KE = 1/2 m v^2; depends on mass and velocity; KE increases with greater mass or greater speed.

Potential Energy (PE)

Energy stored due to position or condition; not changing unless position changes.

Gravitational Potential Energy (GPE)

PE due to an object's height in a gravitational field; U = m g h.

Conservation of Energy

Energy may change form, but the total amount of energy in a closed system remains constant.

Power

Rate at which work is done; P = Work / time; unit is the watt (W); 1 W = 1 J/s.

Thermal Energy

Energy associated with the temperature of a system; related to heat transfer and temperature.

Calorie (cal)

Amount of energy needed to raise the temperature of 1 kilogram of water by 1°C (as noted in the notes).

Watt (W)

Unit of power; equal to 1 joule per second (1 W = 1 J/s).

Joule (J)

Unit of energy; work done by a force of 1 newton acting over 1 meter.

Kilowatt-hour (kWh)

Unit of energy on electricity bills; 1 kWh = 1000 Wh = 3.6 × 10^6 J.

Elastic Potential Energy

Energy stored in deformed elastic objects (e.g., springs, rubber bands).

Chemical Potential Energy

Energy stored in chemical bonds (e.g., fuels, batteries).

Wave Energy

Energy carried by waves, including light and sound waves.

Sound Energy

Kinetic energy associated with the vibration of molecules in a medium; sound waves are longitudinal and require a medium.

Mass Energy (Rest Energy)

Energy inherent to mass; E = m c^2; rest energy is the energy at rest.

E = mc^2

Einstein’s mass–energy equivalence: energy and mass are interchangeable.

Special Relativity

Theory with two postulates: (1) the speed of light is the same for all observers; (2) the laws of physics are the same in all inertial frames.

Postulate 1 (Speed of Light)

The speed of light is constant and the same for all observers, regardless of their motion relative to the light source.

Postulate 2 (Inertial Laws)

The laws of physics are the same in any inertial (non-accelerated) frame of reference.

General Relativity

Theory relating gravity to the curvature of space-time; space-time is unified and gravity can affect light.

Space-Time

The four-dimensional fabric that combines space and time in relativity.

Momentum (Linear)

p = m × v; quantity describing the motion of a body; momentum is conserved in the absence of external forces.

Angular Momentum

Momentum associated with rotation; L = Iω; direction along the axis of rotation; conserved in closed systems.

Rotational Inertia (I)

A measure of an object's resistance to changes in its rotation; depends on mass distribution relative to the axis.

Conservation of Angular Momentum

In the absence of external torque, angular momentum remains constant (e.g., ice skater).

Simple Machines

Devices that change the magnitude or direction of a force (e.g., pulley, lever, inclined plane).

Mechanical Advantage (MA)

The ratio of output force to input force; neglecting friction, input and output work are equal.

Elastic Collision

A collision in which objects bounce without permanent deformation and KE is conserved.

Inelastic Collision

A collision in which objects deform or stick together; some kinetic energy is not recovered.

Simple Pendulum

A system where energy continuously converts between KE and PE; KE is max at the bottom, PE max at the top.

Fossil Fuels

Petroleum, coal, natural gas; carbon-based and nonrenewable; energy stored from ancient sunlight.

Solar Energy

Energy from the sun; a renewable resource with storage challenges.

Energy and Civilization

Sun is the ultimate energy source for most fuels; fossil fuels are finite.

Inertial Frame

A non-accelerating reference frame in which Newton's laws hold true.

Space-Time Warping

A curvature of space-time due to mass/energy, as described in General Relativity.

Kinetic Energy vs Velocity

KE increases with speed; doubling velocity increases KE by a factor of four (for the same mass).