1 On their return from the moon, the crew of Apollo 13 needed to alter the course of their craft to avoid missing the Earth by 99 miles (159 km). Explain how they chose the position to carry out the manoeuvre.
2 The 'burn' was carried out 342000 km away from the Earth, using a rocket with thrust 1240 N. The mass of the whole craft was 30000 kg, its speed 1250 ms -1 . Show that a 14 second burn at right angles to the craft's motion would cause the necessary alteration in its course. [Hint: calculate the change of momentum caused by the burn.]
