Galilei 27 orbiting Iris 2 (part 2)
    Date : May 2008
Author : Camil Cyr, Adaptated by : Caroline Viger
College : Collège de Maisonneuve, John Abbott College
Length : 1 1/2 to 2 hours
Related concept(s) : Circular dynamics (centripetal acceleration), law of universal gravitation, kinematics (1-D), thrust
    The student is the captain of a flight crew on a space ship whose mission is to explore extrasolar planets. The space ship, Galilei 27, is approaching the planet Iris 2 when the on-board computers malfunction. The crew panics.

The student will need to calculate the velocity at which Galilei 27 must be traveling at the time it enters a stable orbit. The next step is to calculate the rate at which the space ship must decelerate in order to approach the planet at the previously calculated velocity, and determine the thrust (force) the motors need to produce this deceleration. In the second part of the exercise, the crew realizes that the motor is roaring louder and louder. The student must recalculate the thrust of the motors at this new altitue as well as reassure the crew.