Glossary
Conservation of Energy
A fundamental law stating that in an isolated system, the total amount of energy remains constant, though it can transform from one form to another.
Example:
In a closed system like a perfectly insulated thermos, the total Conservation of Energy means the heat from hot coffee will eventually spread, but the total energy within the thermos remains the same.
Conservative Forces
Forces for which the work done on an object is independent of the path taken, and mechanical energy is conserved when only these forces are present.
Example:
Gravity is a conservative force because the work done lifting a book to a shelf is the same whether you lift it straight up or take a winding path.
Elastic Potential Energy (Us)
Energy stored in a deformable material, like a spring, when it is stretched or compressed from its equilibrium position.
Example:
A compressed toy dart gun spring stores elastic potential energy that is released to launch the dart.
Energy
The ability to do work. It exists in various forms and is fundamental to understanding how objects move and interact.
Example:
A fully charged battery stores chemical energy that can be converted into electrical energy to power a device.
Gravitational Potential Energy (Ug)
Energy stored in an object due to its position within a gravitational field, dependent on its mass, height, and the acceleration due to gravity.
Example:
A roller coaster car at the top of the highest hill has maximum gravitational potential energy before it begins its descent.
Joules (J)
The standard SI unit of measurement for both work and energy.
Example:
Lifting a 1 kg apple by 1 meter requires approximately 9.8 Joules of work.
Kinetic Energy (K)
The energy an object possesses due to its motion, directly proportional to its mass and the square of its velocity.
Example:
A bowling ball rolling down the lane has significant kinetic energy due to its mass and speed.
Mechanical Energy
The total sum of an object's kinetic energy and all forms of potential energy (gravitational, elastic) within a system.
Example:
A pendulum swinging back and forth continuously converts its mechanical energy between kinetic and gravitational potential forms.
Non-conservative Forces
Forces for which the work done on an object depends on the path taken, leading to a loss or gain of mechanical energy, often converting it into thermal energy.
Example:
Air resistance is a non-conservative force because a skydiver experiences more work done by air resistance on a longer, winding descent than on a direct vertical fall.
Spring Constant (k)
A measure of the stiffness of a spring, indicating how much force is required to stretch or compress it by a certain distance.
Example:
A car's suspension system uses springs with a specific spring constant to absorb shocks from the road.
Thermal Energy (Eth)
Energy associated with the random microscopic motion of atoms and molecules within a system, often appearing as heat or sound due to non-conservative forces.
Example:
When you rub your hands together, friction converts mechanical energy into thermal energy, making your hands feel warm.
Work
The process of transferring energy into or out of a system by applying a force over a distance, specifically when the force has a component parallel to the displacement.
Example:
When you push a heavy box across the floor, you are doing work on the box, transferring energy to it.
Work-Energy Theorem
States that the net work done on an object by all forces acting upon it is equal to the change in its kinetic energy.
Example:
If a car accelerates, the net Work-Energy Theorem tells us that the net work done by the engine and friction equals the increase in the car's kinetic energy.