2005 Hsc (1 Viewer)

[Jaymee]

Does anyone have the answer to Q 19 from the 2005 HSC paper?

In 1970 NASA launched Apollo 13, their third mission planned to land humans on the Moon. Half-way to the Moon a hige explosion crippled the spacecraft. The only way home for the astronauts was to fly around the back of the Moon and then fire the rocket engine to take the craft out of lunar orbit and put it into an Earth-bound trajectory.

At the completion of the rocket engine burn, mission leader Jim Lovell was heard to say, 'We just put Isaac Newton in the driver's seat'.

Given that the spacecraft returned safely to Earth, justify Jim Lovell's statement.

 

[gamecw]

Does anyone have the answer to Q 19 from the 2005 HSC paper?

In 1970 NASA launched Apollo 13, their third mission planned to land humans on the Moon. Half-way to the Moon a hige explosion crippled the spacecraft. The only way home for the astronauts was to fly around the back of the Moon and then fire the rocket engine to take the craft out of lunar orbit and put it into an Earth-bound trajectory.

At the completion of the rocket engine burn, mission leader Jim Lovell was heard to say, 'We just put Isaac Newton in the driver's seat'.

Given that the spacecraft returned safely to Earth, justify Jim Lovell's statement.

Answer

The statement supposed made by Lovell reflects an understanding of physics in that, at the completion of the rocket burn, it will be the gravitational forces acting and the inertial properties of Earth and spacecarft that determine the path followed by the spacecraft. It was Isaac Newton who developed the theory of gravitation to determine the size of the gravitational foce that will act between Earth and spacecraft, i.e. F=Gm1m2/d^2.

Newton also developed his laws of motion that will determine the parh followed by the spacecraft.
1st law: with no rockets the motion will remian constant unless a net force acts
2nd law: the accelertaion of the spacecraft is proportional to the net force acting
3rd law: the rocket produces a reaction force equal and opposite to the gravitational force that Earth creates on it

Considering this, Loveel's comment is valid as it can be seen that it was the gravitional force and resulting change in velocity of the spacecraft that determined its trajectory back to Earth. It was Newton's law that acted to steer the spacecraft safely back to Earth.