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Objectives To understand …… what gravity, mass and weight are. what gravity, mass and weight are. how gravity changes. how gravity changes. how the weight.

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Presentation on theme: "Objectives To understand …… what gravity, mass and weight are. what gravity, mass and weight are. how gravity changes. how gravity changes. how the weight."— Presentation transcript:

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

2 What do gravity, mass and weight all have in common? What do gravity, mass and weight all have in common? Forces can: Forces can: 1. Change speed of an object 2. Change direction of object 3. Change the size or shape of an object FORCES

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

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

5 A downward-pulling force on an object due to gravity. A downward-pulling force on an object due to gravity. Measured in Newtons (N) Measured in Newtons (N) Changes depending on where you are. Changes depending on where you are. Where would the flag be lighter? 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. In order to calculate mass or weight of an object you need the gravitational field strength. On Earth it is approx 10 N/kg On Earth it is approx 10 N/kg WEIGHT= MASS x G.F.S (N)(kg)(N/kg) You need to remember this!!

7 1. Calculate the mass of a book which has a weight of 10N. 2. Calculate the mass of a man who has a weight of 750N. 3. 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? What is gravity again? The force of attraction for a larger object is greater than smaller one. 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 force of attraction between 2 masses decreases as you go further apart. The g.f.s changes on different planets. The g.f.s changes on different planets.

9 Newton said the moon is caught between 2 forces: Newton said the moon is caught between 2 forces: 1. Gravity 2. Centrifugal force

10 As planets get further away from Sun: As planets get further away from Sun: 1. The speed the planet moves. 2. The time to complete an orbit.

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

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