1. Distinguish between inertial and non-inertial frames of reference.
Frames of reference are coordinate systems or objects with respect to which we take measurements. (1)
A non-inertial frame of reference is one that is accelerating with fictitious or inertial forces. In these frames observers have to predicate the existence of these ‘forces’ to maintain the validity of Newton’s laws.
An inertial frame of reference is one that is moving with constant velocity or is it at rest, holding Newton’s first law of Inertia. No frame is more correct then another, however, some are simpler. An example could be the stars.(2)
2. Analyse the changing acceleration of a rocket during launch in ...view middle of the document...
Hence the forces on the astronauts increase. The g-forces increase as minimal friction occurs when the density of the atmosphere decreases with the increasing height of the rocket. (5)
3. Discuss the importance of Newtons law of universal gravitation in understanding and calculating the motion of satellites
Simplistically Newton’s Law of Universal Gravitation is that an object attracts every other object in the universe and the two factors that determine the force of the attraction are:
1. The mass of each of the two objects
2. The distances between their centres of mass.
Represented mathematically by:
where, F = force of attraction between objects
G = universal gravitational constant (which is equal to 6.67 x 10-11 N m2 kg-2)
m1 = mass of object 1
m2 = mass of object 2
d = distance between their centres of mass. (6)
Gravitation provides the centripetal force that produces the circular motion that is the satellite’s orbit around a planet. Therefore, it can be said that:
Gravitational force = Centripetal force
A planet revolving around the sun in a circular orbit or radius r, the centripetal force is provided by the gravitational attraction between the planet and the sun. If the mass of the planet is m and the mass of the sun is M, then:
The following expressions can be derived, from the relationships described in the information above:
The second equation describes the relationship between the radius of an orbit and the period for any (and all) satellites, natural and artificial, orbiting the earth and planets and comets orbiting the sun. It is also Kepler’s third law known as Keplers Law of Periods a necessary consequence of Newton’s Law of Universal Gravitation. (7)
4. Describe how the slingshot effect provides greater speed for space probes
The slingshot effect is also known as a planetary swing by or a gravity-assist manoeuvre. It is performed to achieve an increase in speed and/or a change of direction.
A spacecraft is aimed close to a planet. As it approaches, the spacecraft is caught by the gravitational field of the planet, and swings around it. The speed acquired is then sufficient to throw the spacecraft back out again, away from the planet. By controlling the approach, the outcome of the manoeuvre can be manipulated.
As the probe approaches a planet it is accelerated by the gravitational attraction of the planet, causing it to speed up relative to the planet. As the probe passes the planet, its speed is reduced ,however, relative to the sun, its speed has increased. The probe picks up angular momentum from the planet as it loses an equal amount. (8)
5. Outline the features of the aether model for the transmission of light
The ancient Greeks spoke of the earth as being surrounded by water, then air and...