17/01/08 gravity and space w richards the weald school
TRANSCRIPT
17/01/08
GravityGravityGravity is an attractive force that affects anything with mass:
Note that this force goes both ways – the Earth
is attracted to us.
17/01/08
GravityGravityGravity depends on 2 things:
If you double the distance the
gravitational force divides by 4…
F
F/4
1) The mass of the objects
2) The distance between them
F 2F
If you double the mass of one object
you double the force
17/01/08
Weight vs. MassWeight vs. MassEarth’s Gravitational Field Strength is 10N/kg. In other
words, a 1kg mass is pulled downwards by a force of 10N.
W
gM
Weight = Mass x Gravitational Field Strength
(in N) (in kg) (in N/kg)
To Remember
Weight measured in Newtons
Mass measured in kilograms1) What is the weight on Earth of a book with mass 2kg?
2) What is the weight on Earth of an apple with mass 100g?
3) Dave weighs 700N. What is his mass?
4) On the moon the gravitational field strength is 1.6N/kg. What will Dave weigh if he stands on the moon?
17/01/08
RocketsRocketsWhen a rocket flies away from Earth the force needed to keep it accelerating decreases:
This is because…1) As the rocket gets further away from Earth the force of ______ decreases.
2) As the rocket burns fuel it gets _______, also decreasing the gravity downwards.
Words – gravity, smaller, large, lighter
_____ force needed here
_____ force needed here
17/01/08
Natural SatellitesNatural Satellites
Mercury
MarsJupiter
Saturn
Neptune
Uranus
Pluto
VenusEarth
These planets are all satellites of the sun
17/01/08
Artificial SatellitesArtificial Satellites
1) Observation (e.g. Hubble Space Telescope) – these are in orbit high above the Earth and can observe the universe without interference by the ____________
2) Communications (e.g. ___, phone, car “SatNav” systems) – these satellites are in “geostationary” orbits. This means that the satellite always stays above ____ ____ point on the Earth and takes a ______ to complete an orbit
3) Monitoring (e.g. weather, spy satellites) – these satellites have a “___ _____” orbit and may scan around the Earth several times a day
Artificial satellites have been around for 50 years and have 3 main uses:
Words – the same, atmosphere, low polar, TV, day