1. 23/11/2018
Gravity and Space

2. Note that this force goes both ways – the Earth is attracted to us.
Gravity
23/11/2018
Gravity is an attractive force that affects anything with mass:
Note that this force goes both ways – the Earth is attracted to us.

3. Gravity Gravity depends on 2 things: 2F 1) The mass of the objects F
23/11/2018
If you double the mass of one object you double the force
Gravity depends on 2 things: 2F
1) The mass of the objects F
2) The distance between them
If you double the distance the gravitational force divides by 4… F
F/4

4. Weight vs. Mass
23/11/2018
Earth’s Gravitational Field Strength is 10N/kg. In other words, a 1kg mass is pulled downwards by a force of 10N. W g M
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?

5. Words – gravity, smaller, large, lighter
Rockets
23/11/2018
When a rocket flies away from Earth the force needed to keep it accelerating decreases:
_____ force needed here
_____ force needed here
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

6. Natural Satellites These planets are all satellites of the sun Mercury
23/11/2018
These planets are all satellites of the sun
Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune
Pluto

7. Artificial Satellites
23/11/2018
Artificial satellites have been around for 50 years and have 3 main uses:
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
Words – the same, atmosphere, low polar, TV, day