Homework #3
1. A 1.5 lb rocket is launched from the ground, with zero initial speed, using a
launch rail elevated at an angle of 75° from ground. Its motor provide a thrust
force T = 23 lb for the period of 0 ? t ? 0.2 s and T = 0 for t? 0.2 s. A kinetic
friction coefficient $\mu_k$ = 0.1 exists between the rocket and its launch rail.
Develop a simulation program in Excel that describes the entire flight
trajectory of this rocket, i.e. its x (horizontal displacement) and y (vertical
displacement) vs. time history, if the launch rail's length is set at 2 ft. As
before, you should assume constant gravitational acceleration g = 32.2 ft/s²,
a particle model for the rocket and thrust in the direction of velocity. Air
resistance is NOT negligible during the entire flight, i.e. from ignition (t = 0) till
time of landing (t = $t_r$), and can be represented by a second order model, $cv^2$,
in which v is the speed of this rocket and c = 0.0007 lb-s²/ft². How does the
existence of air drag affect the maximum value of y during the period of 0 ? t
? $t_r$, fight time $t_r$, range x($t_r$) and final speed v($t_r$) of this rocket?
2. Same as problem #1 above except the rocket's trust force is given by T =
23($e^{-150[(t-0.2)^2]^{1.2}}$) lb, in which time t = 0 at the instant of ignition.
