There are two HW problems I just CAN'T seem to solve. Any help you guys could provide would be extremely appreciated!!!


1) The troublesome Mooninites Ignignokt and Err have stolen a rocket from
NASA and escaped to Mars. On Mars, Err opens the classified instruction
documents and learns that this is no ordinary rocket but one with an experimental
engine that provides a time-dependent thrust for exactly 10 seconds after which the
engines shut off completely. The thrust provided by the rocket engines can be
expressed as F(t) = −24t 2 +144t
and is purely in the vertical direction. Up to no good as usual, they decide to fire off
the rocket from the surface of Mars. Neglecting air resistance and assuming the
rocket has a mass of 2kg, how long is the rocket airborne before it crashes back to
the ground and what is the rocket’s maximum elevation?


I've spent two hours attempting to do this problem already and while I know HOW to find height and time (and I know I need to split the problem into two parts), I cannot find acceleration for the first part and I cannot find final velocity for the first part (first part = first 10 seconds).

Last edited by JinFTW (2008-02-21 09:08:01)