Physicists describe certain properties, such as angular momentum and energy, as being conserved. What does this mean? Do these conservation laws imply that an individual object can never lose or gain angular momentum or energy? Explain your reasoning.

The conservation of angular momentum is a fundamental principle in physics. It states that the total angular momentum of an isolated system remains constant. Angular momentum is defined by how an object rotates, and it depends on the object's mass, shape, and speed of rotation. It's like a spinning figure skater who pulls their arms in to spin faster. Even though their speed changes, the total angular momentum stays the same.
When no external torques (twisting forces) act on the system, the angular momentum does not change. For example, in space, where there are no external forces, a planet's rotation remains constant. The same principle applies to a spinning top on a frictionless surface. The top will keep spinning at the same rate unless an external force, like a hand, stops it.

• This principle helps explain many phenomena, such as how stars and galaxies rotate.
• It is crucial in understanding scenarios from atomic scales to astronomical scales.

The conservation of energy principle states that the total energy in an isolated system remains constant over time. Energy can change forms, such as kinetic (motion), potential (stored energy), thermal (heat), etc., but it cannot be created or destroyed.
For instance, when an ice skater glides on the ice, the kinetic energy of movement can convert into thermal energy due to friction. However, the total energy before and after the glide remains the same.

• Consider a roller coaster: as it climbs a hill, kinetic energy is converted to potential energy. At the top, it has maximum potential energy. As it descends, this potential energy converts back to kinetic energy. Despite these changes, the total energy is conserved.

This principle is crucial in various fields, from engineering to natural sciences, ensuring energy calculations balance out in experiments and real-world applications.

An isolated system is one where no external forces or energy enter or leave the system. Because of this, certain properties within the system, like energy and angular momentum, stay constant.
Imagine a sealed container where no particles or energy enter or exit. Whatever happens inside, the total amount of energy and angular momentum remains unchanged.
In reality, perfectly isolated systems are rare, but the concept helps in theoretical physics and understanding real systems that are approximately isolated.

• Examples include planets in space which primarily interact through gravity, or an ice skater in motion with minimal external forces acting on them.
• The idea of isolated systems is fundamental for applying conservation laws effectively in problem-solving.