Transcript 2009_SeeS_OrbitalDynamics_Poster

Centripetal Force
• Centripetal force is the force that keeps
an object rotating in a circle.
• If you spin a ball attached to a string
around your head, the force comes from
the tension of the string.
• The centripetal force points towards the
center of the circle.
Centripetal
Force
• But if it points towards the center of the
circle then why do I feel like I’m being
pushed to the outside?
• This is called the “centrifugal” force,
and is not real.
• Objects want to continue to move in a
straight line, so when they are forced
to turn they resist this change.
• For example, if we cut the rope that is
attached to the ball above, the ball will
not fly away from the center of the
circle but will continue in a straight line.
Planetary Orbits
• Just like the tennis ball above, the planets in our solar system rotate
around the sun.
• The path that these planets follow is called an orbit.
• Instead of a string connecting them to the sun, the force of gravity
between the sun and the planets is what keeps the planets in their
orbit.
• Planetary orbits aren’t always circles.
Sometimes they follow an oval
shape, called an ellipse.
Angular Momentum
• Whenever an ice skater holds their
arms out they can spin around
pretty fast.
• But if they move their arms
towards their body they can spin
around even faster.
Planet
• The planets in our solar
system behave in a similar
manner.
• The planets closer to the sun
move around faster.
• The planets further away
from the sun move slower.
Distance from Days to Orbit Sun
Sun (Earth = 1)
(Earth = 1)
Mercury
0.39
0.24
Venus
0.72
0.62
Earth
1
1
Mars
1.52
1.88
Jupiter
5.2
11.86
Saturn
9.54
29.46
Uranus
19.18
84.01
Neptune
30.06
164.8
Effects in the Solar System
• Ever wonder why comets are only
around for a short time?
• As they get close to the Sun, they
move faster, just like the Skater
drawing in her arms!So when they
are close enough to see, they are
flying by quickly!
Planet
• The planets in our solar
system behave in a similar
manner.
• The planets closer to the sun
move around faster.
• The planets further away
from the sun move slower.
Distance from Days to Orbit Sun
Sun (Earth = 1)
(Earth = 1)
Mercury
0.39
0.24
Venus
0.72
0.62
Earth
1
1
Mars
1.52
1.88
Jupiter
5.2
11.86
Saturn
9.54
29.46
Uranus
19.18
84.01
Neptune
30.06
164.8