Transcript Lesson 4 Types of Satellites and circular motion

Do now!
Can you stick the sheet in
and READ it please?
Satellites
How far could you kick a dog?
From a table, medium kick.
How far can you kick a dog?
Gravity
Harder kick?
Harder kick
Gravity
Small cannon?
Woof!
(help)
Small cannon
Woof!
(help)
Gravity
Bigger cannon?
Bigger cannon
Gravity
Gravity
Even bigger cannon?
Even bigger cannon
Gravity
Gravity
Gravity
VERY big cannon?
VERY big cannon
Gravity
Humungous cannon?
Dog in orbit!
The dog is
now in orbit!
(assuming no
air resistance
of course)
Dog in orbit!
The dog is
falling towards
the earth, but
never gets
there!
Dogs in orbit!
Gravity
The force that
keeps an
object moving
in a circle is
called the
centripetal
force (here
provided by
gravity)
Other examples
Remember they are not this elliptical - GR
Earth’s
gravitational
attraction on moon
Uniform circular motion
The centripetal acceleration/force is always
directed towards the centre of the circle
Centripetal force/acceleration
velocity
Note!

There is no such thing as centrifugal
force! (at least not until you get to
university!)
CENTRIFUGAL
Types of orbits
Geostationary
The satellite orbits once every 24 hours, so
appears to stay above the same point on the
earth’s surface
Looking from
above the North
pole
Geostationary
Useful for communications satellites. Also for
weather over one area.
Polar
Satellite orbits over the poles
Polar
Useful for mapping and remote sensing when
the whole of the earth’s surface needs to be
studied
Some famous satellites
Sputnik (4th October 1957)
Sputnik (4th October 1957)
Russian
 84 kg, 58cm diameter
 800km above the earth
 30 000km/h
 Orbited every 90 mins
 Fell after 92 days

Sputnik 2 (a month later)
Sputnik 2 (a month later)
450 kg
 Carried a dog! (Laika)
 Laika is believed to have died from
overheating in the cabin a few hours
after launch

It’s a dogs life.
Hubble Space telescope
Hubble Space telescope
Launched in 1990
 13.1m long
 Doesn’t have to see through the
earth’s atmosphere

That’s it!
Can you try some questions now?
Page 141 in your book.
 Answer in full sentences please.

TEST next
Thursday 24th
September. Mr
Porter is giving you
a summary sheet
to stick in.