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52 Cards in this Set
- Front
- Back
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What is a satellite and what are the two types? |
An object that orbits a planet in space. Natural- the moon Artificial- put there by humans |
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How is a satellite kept in orbit? |
By gravity providing a centripetal force on the object pulling it toward the centre of the planet. |
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How is gravitational force impacted by distance? |
Force gets weaker as two objects are moved further apart. Inverse square low applies (distance x 3 = 1/9 the force) |
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What does the difference in gravitational force of far away objects mean for satellites? |
-planets closer to the sun travel quicker and have shorter orbital periods -planets further from the fun travel very slowly and have longer orbital periods |
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Describe the difference between periodic comets' and the planets' orbits. |
PC orbit the sun in ellipses Planets orbit the sun in circles |
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Why is the orbit of a comet elliptical? |
When a comet is close to the sun it has to travel very fast to escape the gravitational force, when the comet is further away it travels more slowly because the sun's gravity pulls it back. |
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Describe the characteristics of satellites in low polar orbit. Give their uses also. |
-travel very quickly -go around the earth several times a day Uses: -imaging earths surface -weather forecasting -military use |
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Describe the characteristics and uses of geostationary satellites. |
-orbit much higher above the earth -take 24 hours to orbit earth -have a fixed position on earths equator Uses: -communications (sat tv) -weather forecasting |
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Give some other uses of satellites. |
Scientific research and gps. |
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Why do artificial satellites orbit the earth? |
Satellite would naturally travel in a straight line however earths gravitational force causes it to continually accelerate towards earth preventing it flying off at a tangent. These effects balance causing the satellite to remain in a circular orbit. |
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What are scalar quantities? Give examples. |
Have a size only. -mass -energy -speed -time |
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What are vector quantities? Give examples. |
Have a size and a direction. -velocity -force -acceleration |
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What are projectiles? Give examples. |
Objects fired through the air. Golf balls Footballs Netballs Darts Long-jumpers |
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What is the trajectory? |
The path a projectile takes. |
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What happens if a projectile is launched horizontally on earth and there is no AR. |
It will have a -constant horizon velocity -steadily increasing vertical velocity |
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What effects a projectiles vertical velocity and how? |
Earths gravitational field causes the projectile to accelerate towards the ground. This only affects vertical velocity. |
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What is a parabolic trajectory and how is it caused? |
A downward curving path. The pull of gravity working against a horizontal projection. |
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What allows the greatest horizontal range of a projectile? |
Launching from the right angle (best = 45) |
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Describe Newton's third law of motion? How can this be applied to standing? |
Every action has an equal and opposite reaction. -you exert a force on the ground (your weight) -the ground exerts an equal and opposite force on you (contact force) Gravity pulls you down towards earth and you are pulling the earth towards you. |
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What increases an objects momentum? |
Increase in mass or velocity. |
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What happens during a collision? Give an example. |
The velocities of objects colliding are parallel. E.g. If a lorry crashes into a car then the car hits the lorry with the same force. |
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What is acceleration? What does it cause? |
The rate of change of an objects velocity over time. Many injuries in collisions are caused by rapid acceleration and usually sudden slowing down of the body. |
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How so safety features in vehicles reduce injury? |
By spreading it the acceleration of the vehicle over a greater period of time, reducing momentum. |
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Describe how momentum in conserved during recoil. |
Total momentum of gun and bullet is 0 even when fired. The bullet moves faster but has a smaller mass than the gun so the momentum moves in opposite directions and cancels out. |
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How is momentum conserved in an explosion? |
Momentum of explosion always 0 even during exploding as fragments fly or in opposite directions and cancel out each others momentum. |
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How is momentum conserved in rocket propulsion? |
When a rockets engines fire in space the rocket speeds up but the total momentum in still 0 as the forward momentum of the rocket is cancelled out by the backwards momentum of the gas it fires out. |
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How is momentum conserved during a collision? |
The two momentums of the objects colliding add together to equal the momentum after the collision. |
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What happens in gas particles under higher pressure (in a smaller volume)? |
-same number of particles have less room to move -each particle will collide with the walls more frequently -so the pressure inside the container increases |
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What happens if the temperature of gas particles increase? |
-the particles gain energy -with increased kinetic energy the particles move more quickly -each particle will collide with the wall more frequently and with more force -the pressure on side the container increases |
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What does a rocket need at launch and how is this provided? |
A large force to enable it to accelerate. Provided by the exhaust gases- the force pushing the gas backwards out the exhaust equals the forward force of the gas on the rocket. The fast moving particles in the gas collide with the walls of the rocket producing the force. |
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What type of force is required to launch satellites into space? How is this achieved? |
A very large force achieved by: -a large number of particles in the exhaust ages -the particles moving at high speed |
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How are different frequencies of radio waves affected by the earth's atmosphere? |
Quite short WL (30mhz to 39ghz) pass through atmosphere Frequencies above 30ghz are reduced in strength or stopped by the atmosphere and scattered by rain, dust etc Frequencies below 30mhz are reflected by ionosphere |
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What is diffraction? |
When a wave meets and obstacle or passes through a gap so spreads out. |
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What affects the amount of wave refraction? |
-large gaps allow waves to pass straight through without diffracting -maximum diffraction occurs when the size of the gap is equal to wavelength |
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How do microwaves compare to radio waves, give some uses. |
Higher frequency, shorter wavelength Used to transmit information to orbiting artificial satellites which then retransmit information back to earth. |
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Why are radio waves useful for tv and radio broadcasts? |
Because due to their relatively long wavelengths they can diffract easily to get around obstacles and the horizon. This means radio waves have a very long range. |
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What does the aerial dish receiving microwaves have to be and why? |
Must be larger than the wavelength of the microwaves producing little diffraction, important as microwaves don't diffract well. |
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What happens when a long wavelength radio wave encounters a hill? |
Points on wavefront near hill set off new waves. These waves are curved allowing them to spread around the hill. |
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Why must the receiving dish and satellite be in exact alignment for microwaves? |
Microwaves can only be sent in thin beans when transmitting informal action as they have a short wavelength so cannot diffract much. |
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What is used to pick up radio signal and microwave signal and how are they shaped? |
Radio signal received by aerial, such as a metal rod. Satellite signal only picked up by dish. Dish is curved to focus microwaves onto the receiver at centre. |
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How does light travel? |
Is an electromagnetic wave so is a transverse wave and travels in a straight line. |
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What does wave reinforcement cause? |
Areas of reinforcement where waves add together Areas of cancellation where waves subtract from each other (peak of one wave fills trough of another). |
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How do areas of reinforcement and cancellation effect light and sound waves? |
Sound R- Loud areas C- quiet areas Light R- bright areas C- dad areas |
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When is a stable interference pattern produced? What does this mean for light? |
When wave sources are coherent (have the same frequency, are in phase, have same frequency). Light sources must be monochromatic. |
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When does constructive interfere (reinforcement) occur and what can you see? |
When identical waves arrive at a point in phase. This produces a wave with a large amplitude so you can see bright fringes. |
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When does destructive interference (cancellation) occur and what do we see? |
When identical waves arrive out of phase. The resulting amplitude is 0 so we see dark fringes. |
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In a CI and DI experiment what must the slit be and what would happen if the double salt was replaced with a single slit? |
Above the same width as the light wavelength. Results in a pattern with a much brighter central fringe. |
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What needs to happen when waves have arrived at a point by different paths? |
The path difference needs to be calculated. |
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How does the path difference apply to DI and CI? |
Is an odd number of half wavelengths for DI Is an even number of half wavelengths for CI |
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Describe how polarisation works? |
Only works for transverse waves as oscillations are at 90. Two polarisers are used, one vertical and one horizontal. The VP only lets vertical vibrations through an the rest gets absorbed. The light after this is plane polarised and the glare is greatly reduced. If you want all light to be blocked, a horizontal polariser is then used to block all horizontal vibrations. |
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Why did people think light was a particle? |
Light travels in straight lines and doesn't bend (why we see shadows) this is not like waves. Reflection can be described in terms if light behaving like a particle. |
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Why do people think light is a wave? |
Particle model not accepted among scientists. Light is a wave theory supports by experiments demonstrating diffraction, interference and dispersion (splitting white light into a spectrum) all qualities of waves. |
