Speeding Around the SunSpeeding Around the Sun

Forces acting on the stopperForces acting on the stopper

• Why did I need to continue to use a force on the stopper?

• Gravity pulling down, friction…

Direction of motion

Tension of string

Force from hand

Reflection QuestionsReflection Questions

• If string let go stopper would fly out like marble did with the tape

• Yes stopper is accelerating changing directions!

• Earth (stopper), Sun (straw-Mrs. O’s hand)

Direction of motion

gravity Direction planet would move without the sun’s gravitational pull. This motion is due to the planet’s inertia.

Data TrendData Trend

• Times increased as the length of string increased. Orbital speed should decrease as string length increased.

• Reasons this might not have happened:–Timing and counting issues–Inconsistency of the force used when

swinging the stopper–The string getting tangled with the straw

and or finger

Why did this happen?Why did this happen?

• Farther away from hand – less tension on the string (force)

• Less force then less acceleration – changes directions slower– For planets – farther away from sun, less

gravity – less acceleration

Why did this happen continued…Why did this happen continued…

• Energy!• Farther from hand (the sun) the more

potential energy the object has.• The more potential energy then less

kinetic energy• Less kinetic energy, less speed!• Think of a roller coaster or the homework

assignment on comets, orbit and energy

Planet speedPlanet speed

• Planets closest to sun are the fastest• Planets farthest from sun are the slowest

What is a Satellite?What is a Satellite?

• Satellite: an object that orbits another object in space

• Natural: planets and moons• Artificial: Man made

Why are satellites used?Why are satellites used?

• Communication• Military• Weather• To study and take pictures of the Earth• GPS

Launching a SatelliteLaunching a Satellite

• Launched with a rocket, generally • satellite launch – videos from NASA• Orbits – Orbit demonstration

Just in Case You Wanted to Just in Case You Wanted to Know…Know…

• Rocket goes straight up with satellite and then tilts normally towards the East so Earth’s rotation can give it a boost

• When satellite is horizontal the satellite is released from launch vehicle

Earth

Satellite

Gravitational Force (the centripetal force)

Inertia: Forward Motion

Satellite is falling around the curved Earth

FuelFuel• Satellites only need fuel in orbit to run

instruments, overcome drag due to air resistance (friction), to reposition…

• The higher the altitude the longer it can stay in orbit (less air resistance)

• Types of fuels – solar panels, batteries, fuel cells, nuclear (for missions going to other planets), ion propulsion…

SpeedSpeed• If satellite is closer to Earth its orbital

speed will be faster – just like planets that are closer to the sun

Just in Case You Wanted to Just in Case You Wanted to KnowKnow

• If satellite is 150 miles high – 17,000 mph• If 22,223 miles high – 7,000 mph

– this type of satellite revolve around the Earth once for every rotation of Earth – called Geosynchronous orbit – hover over 1 point of Earth

To Leave OrbitTo Leave Orbit• Satellite should speed up to escape

Earth’s gravity (need to be going at least 25,000 mph!)

• If satellites slow down they will eventually come back down to Earth (will crash or burn up)

Orbiting Another PlanetOrbiting Another Planet

• If satellite goes by another planet at a close enough distance and a specific speed the satellite will be pulled in by the planet’s gravity and will begin to orbit that planet

• Probably will be different speeds/distances then when orbiting Earth

• Mars Orbiter – videos from NASA