1. 3. The solar system is held together by gravity
Caroline Chisholm College
Physics
3. The solar system is held together by gravity

2. Caroline Chisholm College Physics
Describe a gravitational field in the region surrounding a massive object in terms of its effects on other masses in it
A gravitational field is a field within which any mass will experience a gravitational force.
The gravitational field around a planet has a radial pattern similar to the electric field around a negative point charge. The field lines are in the direction towards the centre of the planet and the closer field lines represent the stronger gravitational field. The presence of another mass (such as a moon) effects the field lines in a way which is similar to the presence of another negative charge. (see Jacaranda p.5 for a diagram)
Present information and use available evidence to discuss the factors affecting the strength of the gravitational force
relationship of weight and distance
The strength of the gravitational force
depends on the mass of the central object,
the mass of the object experiencing the
force, and on the distance between the
two objects.
A larger mass of either object
increases the gravitational force and
increasing the distance decreases the
gravitational force.

3. Caroline Chisholm College
A gravitational field is a field surrounding a massive object, within which any other mass will experience a gravitational force. This force is a force of attraction - the greater the mass, the greater the gravitational attracting force.
Caroline Chisholm College
Physics
The gravitational field around a planet has a radial pattern similar to the electric field around a negative point charge. The field lines are in the direction towards the centre of the planet and the closer field lines represent the stronger gravitational field. The presence of another mass (such as a moon) effects the field lines in a way which is similar to the presence of another negative charge. (see Jacaranda p.5 for a diagram)
The strength of the gravitational force depends on the mass of the central object, the mass of the object experiencing the force, and on the distance between the two objects.
A larger mass of either object increases the gravitational force and increasing the distance decreases the gravitational force.
Describe a gravitational field in the region surrounding a massive object in terms of its effects on other masses in it
Use available evidence to discuss the factors affecting the strength of the gravitational force

4. everything attracts everything
Caroline Chisholm College
Physics
Define Newton's Law of Universal Gravitation
( the law)
everything attracts everything
(NOT the law)
Solve problems and analyse information using
Jacaranda
Chapter 4

5. Caroline Chisholm College Physics
where F = gravitational force between two objects
G = universal gravitational constant = 6.67 x 10-11
m1= mass of object 1
m2= mass of object 2
d = distance between the two centres of mass
Define Newton's Law of Universal Gravitation
Solve problems and analyse information using
Try Jacaranda
p.57 onwards

6. Caroline Chisholm College
Physics
Discuss the importance of Newton‘s Law of Universal Gravitation in understanding and calculating the motion of satellites
remember r = rE+ altitude
So high altitude (e.g. geostationary) orbits are lower velocity
and low altitude (e.g. low Earth) orbits are higher velocity

7. Caroline Chisholm College
Newton’s Law of Universal gravitation allows us to calculate the gravitational force experienced by a satellite at any altitude. We understand that this gravitational force is the centripetal force that keeps the satellite in its orbital motion. We can equate the two expressions for force to calculate the orbital velocity of the satellite. We therefore know all quantities (e.g. angular velocity, period etc.) that relate to the uniform circular motion of the satellite.
Caroline Chisholm College
Physics
Discuss the importance of Newton‘s Law of Universal Gravitation in understanding and calculating the motion of satellites
remember r = rE+ altitude
So high altitude (e.g. geostationary) orbits are lower velocity
and low altitude (e.g. low Earth) orbits are higher velocity

8. current technology could reach 100,000 km/h
Extended space travel requires
reliable power,
high velocity and a means of communication
Caroline Chisholm College
Physics
Voyager 1 (1977)
11.9 billion km from sun
62000 km/h
current technology could reach 100,000 km/h
Using planetary slingshot assistance
24 days to Mars (our nearest neighbour)
5 years to Neptune (outer edge of solar system)
46,000 years to the closest star, Proxima Centauri
52,000,000 years to the closest edge of our galaxy
24 billion years to the closest galaxy, Andromeda
or 2.25 million yrs at the speed of light!

9. Caroline Chisholm College
Identify that a slingshot effect can be provided by planets for space probes
Caroline Chisholm College
Physics
Planetary swing-by to pick up speed by gaining K.E. from the planet (which consequently loses a bit of speed)
Interaction behaves as an elastic collision Vi vi
Conservation of momentum and
conservation of kinetic energy gives
vf = vi + 2Vi Vf
N.B. this is the maximum result and will be less if not head-on interaction 10 1
satellite approaches planet at relative velocity of 11 so it will bounce off at 11 relative to planet 21
11 relative to the planet is 21 relative to the sun

10. Caroline Chisholm College
The slingshot effect is a planetary swing-by to pick up speed by gaining K.E. from the planet (which consequently loses a bit of speed)
Caroline Chisholm College
Physics
The interaction behaves as an elastic collision Vi vi
Conservation of momentum and
conservation of kinetic energy gives
vf = vi + 2Vi Vf
E.g. The satellite (moving at 1 relative to the sun) approaches the planet at a relative velocity of 11 so it will bounce off at a velocity of 11 relative to planet
N.B. this is the maximum result and will be less if it is not a head-on interaction 10 1 21
Identify that a slingshot effect can be provided by planets for space probes
11 relative to the planet is 21 relative to the sun!