Gravity : 20/04/2009 Gravity Gravity is an attractive force that affects anything with mass:
Gravity : 20/04/2009 Gravity Gravity depends on 2 things: 1) The mass of the objects 2) The distance between them
Weight vs. Mass : 20/04/2009 Weight vs. Mass Earth’s Gravitational Field Strength is 10N/kg. In other words, a 1kg mass is pulled downwards by a force of 10N. Weight = Mass x Gravitational Field Strength
(in N) (in kg) (in N/kg) What is the weight on Earth of a book with mass 2kg?
What is the weight on Earth of an apple with mass 100g?
Dave weighs 700N. What is his mass?
On the moon the gravitational field strength is 1.6N/kg. What will Dave weigh if he stands on the moon?
Rockets : 20/04/2009 Rockets When a rocket flies away from Earth the force needed to keep it accelerating decreases: Words – gravity, smaller, large, lighter
Natural Satellites : 20/04/2009 Natural Satellites Mercury Mars Jupiter Saturn Neptune Uranus Pluto Venus Earth These planets are all satellites of the sun
Slide 7: 20/04/2009 Artificial 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