Unit 2 (Chapters 5-7) Flashcards
(25 cards)
What is the acceleration of gravity on earth’s surface?
9.8m/s^2
What is inertia?
This is the property where the motion of an object will continue until something (friction) changes it.
What are Newton’s 3 laws of motion?
- A body continues at rest or in uniform motion in a straight line unless acted on by an external force
- The acceleration of a body is inversely proportional to it’s mass, directly proportional to the force, and in the same direction as the force.
- To every action there is an equal opposite reaction
What is the inverse square law for gravity?
The idea that the strength of an effect (gravity) decreases in proportion as the distance squared increases. i.e. the earth’s gravity affects the moon more than it does the sun because the moon is much closer to earth than the sun.
What is mutual gravitation?
The idea that objects in the universe attract each other (pull on each other). Just as the earth’s gravity pulls on the moon, so to does the moon’s gravity pull on the earth.
What are the three principles which define orbits?
- An object orbiting earth is actually falling towards earth’s centre. The object continually misses colliding with earth because of it’s lateral orbital velocity
- Objects orbiting each other are revolving around their mutual centre of mass which is the balancing point between the two systems of force acting on each other
- There are two types of orbits
- Closed orbit is a repeating cycle, the object returns to its starting point. This can be either circular or elliptical.
- Open orbits: an orbit that does not return to its starting point; if it reaches it’s escape velocity it becomes an escape orbit.
How does mass and radius relate to escape velocity?
Higher mass with large radius objects have low escape velocities, lower mass objects with small radius have larger escape velocity.
What is angular momentum?
Angular momentum is the combination of the objects mass with it’s speed of rotation or revolution.
What is Newton’s version of Kelper’s 3rd law and why is it significant.
Newtons version of Kelper’s third law states that you can measure masses through the objects orbital period and orbital radius.
This is significant because it is one of the only precise ways to measure masses of objects in the universe.
Explain why the oceans have tides.
The moon’s gravity pulls on the water on the near side creating one tidal bulge and then the earth’s centre pulls the earth away from the water on the far side, creating a second tidal bulge
What are the two postulates of Einstein’s theory of relativity?
First Postulate: The principle of relativity is that observers can never detect their uniform motion except relative to other objects. We can detect accelerated motion.
Second Postulate: the speed of light in a vacuum is constant and will have the same value for all observers independent of their motion relative to the light source.
What is the general theory of relativity?
“The basic idea is that instead of being an invisible force that attracts objects to one another, gravity is a curving or warping of space. The more massive an object, the more it warps the space around it.”
According to the general theory of relativity, mass tells space time how to curve and the curvature of spacetime (gravity) tells mass how to accelerate.
What is electromagnetic radiation?
Another word for light. It is something that is made up of both electric and magnetic feilds. Electromagnetic radiation travels at the constant speed of 3x10^8m/s.
How is light described?
Light is described via wavelength (distance between peaks of waves) and frequency (number of waves/second)
Short wavelengths carry more energy than long wavelengths
A photon is a particle of light (i.e. a packet of waves)
Which light has the shortest wavelengths? The longest?
Shortest include gamma rays, x-rays, and UV rays.
Longest includes Radio waves and microwaves
What is an atmospheric window?
Wavelengths regions in which Earth’s atmosphere is transparent.
Earth’s atmospheric window allows visual light, infrared and radio waves through
What are the two types of telescopes and how do they work?
A refracting telescope (uses lenses to gather and focus light)
A reflecting telescope (uses a mirror to gather and focus light)
What is a drawback of refracting telescopes?
They are prone to optical distortion which limits their use because the glass refracts different wavelengths at different angles leading to chromatic aberration (colour separation)
What are the three powers of a telescope which describe their capabilities?
- Light gathering power: how much light is the telescope able to gather.
- Resolving Power: how much fine detail the telescope can reveal
- Magnifying power: how much bigger the telescope can make the image.
What is an atom?
Atoms are made up of a proton, neutron, and electron, all contained in the nucleus. Therefore the nucleus makes up most of he atom’s mass.
The nucleus sits in an sphere of empty space akin to an apple seed sitting in the centre of a football stadium
The number of protons an nucleus has determines which element the atom is. The number of neutrons can vary with more neutrons creating heavier versions of an element. Isotopes are atoms with extra neutrons
Ions are atoms who have gained or lost an electron. The size of an electrons orbit is related to the energy that binds it to the atom. Closely orbiting electrons are more tightly bound (and require more energy to separate) than farther orbiting electrons.
What is Quantum mechanics? What is an example?
The laws that describe how atoms behave.
e.g. Permitted orbits is a law that says atoms can only have certain amounts of binding energy which means the electrons can only have orbits of a certain size.
What is the difference between a ground state atom and an excited atom?
A ground state atom is in its smallest and most tightly bound state. This atom is at its lowest energy level.
An excited atom is an atom moving to a higher energy level. Atoms can be excited by:
- a collision with another atom
-absorbing a photon (with precisely the right amount of energy)
Excited atoms are unstable and must give up the excess energy by emitting a photon of light
Each type of atom has a unique set of energy levels so each type absorbs and emits photons with a unique set of wavelengths. (this means you can identify the makeup of an object based on the wavelengths of it’s light.
What are the three types of spectra?
- Continuous spectra: a spectrum which there are no absorption or emission lines
- Emission Spectra: a spectrum where photons are emitted by excited gas. This creates emission lines (bright lines) on the spectrum.
- Absorption Spectra: when radiation passes through a cool gas so atoms in the gas absorb photons of a certain wavelength. This creates absorption lines (dark lines) in the spectra.
Essentially emission and absorption lines represent a transition between energy levels
What are Kirchhoff’s Laws to describe spectra?
Law 1: The continuous spectrum
- A solid liquid or dense gas excited to emit light will radiate at all wavelengths and produce a continuous spectrum
Law 2: The emission spectrum
- A low density gas excited to emit light will do so at a specific wavelengths and thus will produce an emission spectrum
Law 3: The absorption spectrum
- if light comprising of a continuous spectrum passes through a cool low density gas, the result will be an absorption spectrum
