Conservation Laws:
state that a particular measurable property of an isolated physical
system does not change as the system evolves over time. In layman terms: the total momentum of all interacting objects always stays the same.
Conservation of momentum
Newton’s cradle (more commonly known as clacker balls) is a prime example of the law of conservation of momentum. The law states that when two objects collide, the total momentum of the objects before the collision is equal to the total momentum after the collision. As the first ball collides with the second ball it transfers momentum to it, and this continues along the line until it reaches the last ball. When the last ball swings into the air, it is demonstrating this concept of conservation as in theory, it would swing out the same distance as the first ball. However, due to friction and air resistance, it does not quite reach its maximum potential, and some momentum must be transferred to air particles.
Law of
conservation of angular momentum
Angular momentum is similar to linear momentum, except it is moving on
a curved path. Unless an external torque
is applied, the total angular momentum in a system never changes. Torque is when force rotates an object around
its center, by twisting. Changes in
angular momentum can only occur through a transfer of momentum with another
object.
An ice skater spinning on her skates with her arms extended is an
example of angular momentum. Her angular
momentum is conserved while she spins.
As she pulls her arms closer in, she spins faster.
Conservation
of Energy
Energy is a rather broad term. Here is a link to the Merriam-Webster definition Energy Definition . Essentially, energy is the ability to do work. Its units are either in calories or joules. All energy in the universe can be traced back to the Big Bang. Therefore,it is clear that energy is always conserved, and cannot be created nor destroyed. However, energy does have the ability to transfer objects and change in form.
3 forms of energy
1. Kinetic- Energy of motion
a. Thermal/heat- the collective kinetic energy of the many individual particles moving randomly within a substance
2. Potential- Stored energy, which may later be converted into kintetic or radiative energy
a. Gravitational- Depends on an objects mass, and how far it can fall as a result of gravity
b. Mass energy-Mass itself is a form of potential energy
3. Radiative- Energy carried by light
Examples of energy transformation
Example A: A rock placed on a tall cliff has potential energy due to the height at which it is placed. If the rock starts to fall, its potential energy is changed to kinetic energy since the rock traded in the height of its position for velocity of its movement.Example B: The mass-energy in the core of the sun is converted into radiative energy (sunlight), which is used to warm us here on Earth so that we can go about our daily lives
Tying it all together: Conservation Laws in Astronomy
What keeps the earth orbiting the Sun? (Same for other planets and stars)
Conservation of momentum: Ultimately this is Newton's first law, and is the reason why Earth will remain in motion unless acted upon by an outside force.
Angular momentum: Helps explain why the Earth always rotates once every 24 hours, and why its rotation axis remains (relatively) fixed in space as it orbits the Sun. The fact that planets are changing direction (more specifically their velocity) over time means that some force must be acting on them to change their momentum. This force is that of the gravity from the sun, but ultimately there is no change in angular momentum, because there is no net torque.
Conservation of energy: As previously stated, the closer an object is to its axis, the faster it will move. Conservation of energy helps explain why the earth moves slower when farther from the sun (because it has more gravitation potential energy, and less kinetic energy).
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