1) Gravity is the force of attraction between two masses, and it causes weight, which is the downward force on objects. Mass stays the same anywhere, while weight depends on location. 2) The weight of an object can be calculated using the formula: Weight = Mass x Gravitational Field Strength. On Earth, gravitational field strength is about 10 N/kg. 3) Gravity decreases with distance from a large mass like Earth or the Sun. Planets further from the Sun move slower and have longer orbits. Satellites orbit Earth in different patterns depending on their purpose.

1. Objectives To understand …… what gravity , mass and weight are. how gravity changes. how the weight changes of an object. what affects gravity. orbits of planets and satellites. Gravity and Space

2. What do gravity, mass and weight all have in common? Forces can: Change speed of an object Change direction of object Change the size or shape of an object FORCES Gravity, Mass and Weight

3. Force of attraction between 2 masses. Not just on Earth but everywhere It can only pull not push. Acts towards centre of Earth.

4. Amount of MATTER in an object. Measured in kilograms (kg). 4 kg 0.1 kg Not to scale Stays the same anywhere you go.

5. A downward-pulling force on an object due to gravity. Measured in Newtons (N) Changes depending on where you are. Where would the flag be lighter? On Earth On Moon

6. In order to calculate mass or weight of an object you need the gravitational field strength. On Earth it is approx 10 N/kg Calculating Weight and Mass WEIGHT= MASS x G.F.S (N) (kg) (N/kg) You need to remember this!!

7. Calculate the mass of a book which has a weight of 10N. Calculate the mass of a man who has a weight of 750N. What is the weight of a pushchair which has a mass of 7kg? REMEMBER the gravitational force strength is 10N/kg on Earth. WEIGHT= MASS x G.F.S (N) (kg) (N/kg)

8. What is gravity again? How does Gravity change? The force of attraction for a larger object is greater than smaller one. The force of attraction between 2 masses decreases as you go further apart. The g.f.s changes on different planets.

9. Newton said the moon is caught between 2 forces: Gravity Centrifugal force Sir Isaac Newton

10. As planets get further away from Sun: The speed the planet moves . The time to complete an orbit .

11. Polar satellites – e.g. weather. Travel in low polar orbit. They pass continuously over north and south poles. Geostationary satellites – e.g. comunication and navigation. Travel at same speed as Earth.