Flashcards in Physics2 Deck (64):
What is relationship between direction of movement and direction of energy in a transverse wave?
They are at 90 degrees to each other
What are the two sections in a longitudinal wave?
Compressions and rarefactions
What is the relationship between the direction of particle movement and direction of energy in a longitudinal wave?
They are parallel
What is a waves purpose?
To carry energy and information from one place to another
What type of wave is sound?
What is a mechanical wave?
A wave that physically vibrates particles. These waves require a medium to go through(require particles to travel)
What are electromagnetic waves?
Disturbances in electrical and magnetic fields. Therefore, they require no particles to travel
How would you describe Amplitude (A)?
The distance between a trough or peak of a wave. It is the maximum displacement of a wave
What is the time period of a wave?
The time taken for one complete wave cycle- T(s)
What unit is wavelength (λ) measured in?
How do you define frequency (Hertz)?
The number of wave cycles (oscillations per second)
e.g. 1Hz = 1 cycle per second
What is wave velocity (m/s)?
The speed of a wave in a given direction
How do you calculate frequency?
1 divided by time base (T)
How do you calculate wave velocity (m/s)?
frequency(Hz) x wavelength(m)
What is the speed of light in a vacuum?
3 x 10^8 m/s
How can waves be generated?
Using a signal generator or other generators such as a microphone which turns kinetic moving particles into an electrical signal
How can sound waves be output?
Using a loudspeaker which turns an electrical signal into kinetic particle vibrations (sound waves)
On what can waves be displayed for analysis?
A Cathode Ray Oscilloscope Screen
What does the height of the square on a CRO represent?
The Y gain- tells you how many volts each height of square is worth (V/cm)
What does the width of a square on a CRO represent?
The time base. It tells you how many seconds each width is worth (s/cm)
How can you work out the time for one complete wave cycle on a CRO?
Time base x squares per oscillation - seconds
How can you work out the amplitude for a wave on a CRO?
Y gain x displacement (in squares) - volts
On a sound wave, what does amplitude represent?
Volume of sound (high amplitude = high volume) - loundness
On a sound wave, what does the frequency represent?
The pitch of the sound (high frequency = high pitch)
What is gravity?
A concept that states all objects with masses will attract each other with a gravitational force
What is weight?
The force due to gravity on an object
What is an orbit?
A circular/elliptical path a mass takes around another mass e.g. satellites around planets
planets around stars
What is the relationship between direction of travel and the centripetal force during circular motion?
They are at 90 degrees to each other
What keeps an object in orbit?
The force due to gravity(F)- centripetal force
What conclusion can be made from the orbital shape of planets in the Milky Way?
The further the planet is away from the Sun, the more elliptical the orbit
How do planets speeds vary in an elliptical orbit?
At the squashed axis, the planet moves faster because it is nearest the source so it has more gravity
How many Newtons per kilogram does each kilogram of mass get pulled by on Earth>
8 N/kg (gravitational field strength)
What is the relationship between gravitational field strength and mass of object causing gravity?
The more the mass of the object causing gravity, the greater the gravitational field strength. e.g. Moon= 1.2N/kg and Mars=3N/kg
What happens to an object if the centripetal force is removed?
The object continues into the direction of travel
Why are sling shots orbits used?
To send probes into deep space by using the gravitational pull of other planets to build up enough speed
How are distances measured in the Milky Way solar system?
Using Astronomical Units (AU) - 1AU = 1 Sun-Earth distance
What is a light year?
The distance that light travels in a year (used for very large space distances)
How many light minutes is the Sun away from us?
8 light minutes
What do telescopes enable us to do?
See objects that are a long distance away
What are the parts of the electromagnetic spectrum different telescopes can "see"?
Gamma rays, X-Rays, Ultra Violet, Visible, Infra Red, Microwaves, Radiowaves
What is an optical telescope?
A telescope that uses visible light to see objects a long distance away
What is a galaxy?
A formation of stars held together under gravity
What is the explanation behind the big bang theory?
Distant galaxies appear to be moving away from each other at an ever increasing rate. Therfore, there must have been a large explosive force to push the galaxxies in the first place - around 13.7 billion years ago
What else can the big bang theory tell us about the size of the universe?
It is constantly expanding
What are the problems with ground based telescopes?
-A big one is needed to capture enough light for a good photo
-They are sensitive to environment. Must be high up above weather and where there is little light pollution
-Earth's atmosphere interferes with some telescopes as it absorbs lots of the IR and UV light
-Earth's atmosphere can lead to distortions and cintillation
Why do stars produce heat and light?
Because of a reaction at their core called nuclear fusion
What is the process of nuclear fusion?
Hydrogen nuclei are forced together under high heat and pressure (due to force). As the helium nucleus is formed from this reaction, massive amounts of energy are released, including heat and light
What is the human range of hearing?
Between 20Hz and 20,000Hz
What are sounds below 20Hz?
What are sounds above 20,000Hz called>
What are the uses for Ultra Sound?
-seeing/scanning for fetus
-seeing muscle tears/tendon inuries
How long does it take for the moon's orbit of Earth to take?
28 days roughly
How fast does the moon rotate on its own axis?
At the same rate at which it orbits the Earth, 28 days
Do we see every side of the moon?
No, we only see the same side of the moon because its orbital period of Earth and rotating speed are syncronous
Why do we see the moon?
Because the Sun's light reflects off of it's surface
What are the types of moon phases?
New moon (0), Crescent Moon(1/4), Half moon (1/2), Gibbous moon (3/4) and full moon (1)
What is a lunar eclipse?
When the moon passes into the Earth's shadow at the correct alignment with the Sun and Earth
What is a solar eclipse?
When the moon blocks some light from the sun reaching the Earth, creating umbra (black) and penumbra regions (slightly light)
What is a comet?
A body in a solar system that is primarily made of rock and ice
Why does a comet have an acoma?
Because as the comet approaches the star the ice melts leaving debri behind it
What shape orbit does a comet have?
A very elliptical one (in our solar system they go out to Kuiper belt and back to sun )
In what substance does sound travel fastest in and why?
A solid because the particles are closer together so it is easier to transfer vibrations 3-5000 m/s
How does the magnetic field in a solenoid differ from that in a magnet?
The magnetic field flows inside the solenoid as well