Presentation on theme: "Gravity and Space Objectives To understand ……"— Presentation transcript:
1 Gravity and Space 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.
2 Gravity, Mass and Weight What do gravity, mass and weight all have in common?Forces can:Change speed of an objectChange direction of objectChange the size or shape of an objectFORCES
3 Gravity Force of attraction between 2 masses. Not just on Earth but everywhereIt can only pull not push.Acts towards centre of Earth.
4 Mass Amount of MATTER in an object. Measured in kilograms (kg). Not to scale4 kg0.1 kgMeasured in kilograms (kg).Stays the same anywhere you go.
5 WeightA 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 Calculating Weight and Mass In order to calculate mass or weight of an object you need the gravitational field strength.On Earth it is approx 10 N/kgWEIGHT= 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 How does Gravity change? What is gravity again?The force of attraction between 2 masses decreases as you go further apart.The force of attraction for a larger object is greater than smaller one.The g.f.s changes on different planets.
9 Sir Isaac Newton Newton said the moon is caught between 2 forces: GravityCentrifugal force
10 Orbits As planets get further away from Sun: The speed the planet moves .The time to complete an orbit .
11 Satellites 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.