Louis Lackey Day 5

Louis Lackey

Day 5 Notes

Perihelion is closest to the sun

Aphelion is farthest from the sun

An ellipse is an oblong circle drawn with two foci points.

The lecture began with physics. Physics is the study of motion. The first document on theoretical physics was Newton's Philsophae Naturalis Principia Mathmatica.

Newton's first law- if an object experiences no net force, then its velocity remains constant- an object at rest remains at rest, an objects in motion remains in motion.

Second- the acceleration of a body is parallel and directly proportional to the net force F acting on the body, is in the direction of the net force, and inversely proportional to the mass m of the body. F=ma.

Third- the law of action and reaction. For every action there is an equal and opposite reaction. Newton's law of universal gravitation states F=G M,1M,2/R^2.

Constant velocity is indistinguishable from rest.

Force changes constant velocity

For every action, there is equal and opposite reaction

The law of force for sun and planets, Gravity is directly proportional to masses, inversely proportional to distance squared.

Newton's law of gravity does not apply to Mercury, Einstein's laws work.

The laws of physics are decided by physicists. They change when new knowledge is available. The predictions are validated only by observation.

Chapter 4.1 Motion

speed is the rate an object moves. speed=distance/time. 10 m/s

velocity is speed and direction. 10 m/s due east

acceleration is change in velocity. M/s^2 “per second per second”

all falling objects fall at the same rate, not counting air resistance.

On earth, G=10 m/s^2.

Force=Mass*acceleration

Momentum=mass*velocity

A net force changes momentum, which generally means an acceleration

rotation or spinning or orbiting is known as angular momentum

net force is overall force

mass is a measure of matter

weight is the force of gravity upon an object, on a scale for example.

Astronauts are not outside of earth's gravity, they are constantly falling, in a circle of orbit. Free fall.

Chapter 4.2 Newton

Newton's work showed that the same laws apply in space and on earth, uniting them in one universe

Newton's laws, as above

Chapter 4.3 Conservation

momentum doesn’t change unless something acts on it

interacting objects exchange momentum through equal and opposite forces

angular momentum=mass*velocity*radius

the angular momentum cannot change unless an external twisting force (torque) is acting on it

earth experiences no torque, so its rotation and orbit will continue indefinitely

energy makes matter move

energy is conserved, but can be transferred and converted

Energy cannot be created or destroyed.

kinetic energy is motion

radiative energy is light

potential energy is stored

thermal energy is the collective kinetic energy of particles; movement.

Thermal energy is a measure of total energy, temperature is a measure of the average. Thermal energy depends on density

gravitational potential energy, on earth, depends on mass, gravity (10 m/s^2), and the distance the object could fall

In space, an object or cloud's potential energy increases when it is spread out. A contracting cloud converts gravitational energy to thermal energy.

Mass is energy, E=mc^2. Energy and mass can convert to each other, such as nuclear weapons or power and particle accelerators.

Chapter 4.4 Gravity

Gravity explained above

the moon pulls on water creating tides. But it happens on both sides. Think about a rubber band, if you pull on one side, the opposite side relatively moves to the center.