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 object
Change direction of object
Change the size or shape of an object
FORCES

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

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

5. Weight
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. 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/kg
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. 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:
Gravity
Centrifugal 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.

12. Comets