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Comets.
Like
planets,
comets orbit the Sun.
Unlike a planet, the orbit of
a comet is often
highly elliptical and may be very, very long.
A comet can only be seen when it is near
our solar
system,
close to the
Sun.
At other times the comet is
too far away to be seen.
The speed of a comet
changes during its orbit.
As the comet gets closer to the Sun,
the Sun's gravity pulls the comet
towards it and the
comet
gets
faster. Also, the gravitational forces become
stronger as the comet gets
closer to the Sun. The comet
is travelling at its fastest when it is closest to the Sun.
As the comet moves away from
the Sun, the reverse
happens.
The Sun's gravity pulls the comet
backwards
and slows it down. The gravitational forces become
weaker
as the comet gets further away. The comet is
travelling at its slowest when it is furthest from the Sun.
In energy terms, the
movement of the comet is similar
to a swinging pendulum or
bouncing ball.
When the comet is closest to the Sun,
it has its maximum kinetic energy
and minimum gravitational potential energy.
When the comet is furthest
from the Sun,
it has its minimum kinetic energy
and maximum gravitational potential
energy.
Links
The Solar System
Revision Questions
gcsescience.com Physics Quiz Index Solar System Quiz gcsescience.com
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