Which is Not Conserved? Practice Quiz

In inelastic collisions, some of the kinetic energy is transformed into other forms of energy such as heat or sound, so it is not conserved. However, momentum and charge remain conserved in a closed system.

Linear momentum is always conserved in collisions regardless of whether they are elastic or inelastic. In contrast, kinetic and mechanical energy are only conserved in elastic collisions.

The law of conservation of energy asserts that energy cannot be created or destroyed, only converted from one form to another. This principle is fundamental in understanding how closed systems behave.

Conservation laws simplify problem-solving by providing relationships between a system's initial and final states. They are critical tools that help verify the consistency and correctness of solutions in physics.

In a closed system with no external forces, the total momentum remains unchanged over time. This concept is fundamental when analyzing collisions and other interactions in physics.

In perfectly inelastic collisions where objects stick together, linear momentum is conserved even though some kinetic energy is lost. This makes momentum conservation the primary tool for determining the final state.

When the skater pulls her arms in, her moment of inertia decreases, resulting in an increase in angular velocity to conserve angular momentum. This is a classic example of how rotational motion adjusts to maintain a constant angular momentum in a closed system.

When external torques are applied, they change the angular momentum of the system, meaning it is no longer conserved. The presence of an external influence disrupts the internal balance required for conservation.

In nuclear reactions, mass can be converted to energy and vice versa, so mass alone is not conserved. Instead, the principle of mass-energy equivalence ensures that the total energy, which includes the mass energy, is conserved.

During chemical reactions, even when electrons are transferred between atoms, the overall net electric charge of the system remains unchanged. This reflects the fundamental conservation law of charge.

Air resistance is a non-conservative force that converts some of the mechanical energy into thermal energy. As a result, the sum of kinetic and potential energy (mechanical energy) decreases even though the total energy remains conserved.

A pendulum in a vacuum does not lose energy to air resistance, so the total mechanical energy (the sum of kinetic and potential energy) remains constant. At the highest point, the energy is all potential, while at the lowest, it is all kinetic.

Elastic collisions are defined by the conservation of both linear momentum and kinetic energy. This distinguishes them from inelastic collisions where kinetic energy is partially converted into other forms.

Although kinetic energy decreases due to its conversion into sound and thermal energy, the total energy of the system remains constant. This overall energy conservation includes all forms of energy present in the system.

In collisions that involve significant deformation (inelastic collisions), momentum is conserved even though kinetic energy is not. This makes momentum conservation the most reliable principle for predicting the outcome of such events.

In the absence of external forces, both linear and angular momentum remain conserved. These conservation laws allow us to analyze the motion of all fragments after an explosion even though kinetic energy may not be conserved.

Even though photons have no rest mass, they carry momentum. The recoil of the atom is determined by the conservation of linear momentum, which ensures that the momentum lost by the photon is balanced by the momentum gained by the atom.

The rocket's acceleration is a result of momentum conservation: as fuel is expelled in one direction, the rocket gains momentum in the opposite direction. This reaction force, explained by Newton's third law, is at the heart of rocket propulsion.

When internal energy is converted into mass, the traditional conservation of mass no longer holds separately. Instead, the mass-energy equivalence principle ensures that the total energy, which includes the newly converted mass energy, is conserved.

According to the conservation of angular momentum, if the moment of inertia decreases without any external torque, the angular velocity must increase. This principle is observed in scenarios such as a figure skater spinning faster when pulling in her arms.