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--- course_planning:computation:scratch_work [2016/03/12 22:44] – [Project 2: Part B: Escape from ice station McMurdo] obsniukm
+++ course_planning:computation:scratch_work [2016/03/25 18:40] (current) – [Code] obsniukm
@@ Line 18: / Line 18: @@
 Just as you are about to radio the time to jump to the runaway researcher, you realize the steering and acceleration controls have become frozen on your hovercraft and so it continues to accelerate and you cannot change direction. 200m ahead of the point at which you were going to tell the researcher to jump is an ice ravine. At the bottom of the ice ravine, 400m below, is an unfrozen salt water pool surrounded by stalagmites. From the ravine's edge to the pool is 490m and the pool stretches for 900m. You are moving too quickly to survive jumping off the hovercraft, but might survive the fall into the pool by staying on the hovercraft; it has seat belts. You now have a choice to make, to stay on your hovercraft or jump to the runaway researcher's hovercraft. One or both may make it to the pool. Your choice may be the difference between life and death.
-====== Project 2: Part C: Escape from ice station McMurdo ======
+====== Project 2: Part C ======
 Surprisingly enough hovercrafts are an expensive piece of kit. Your employer, the Carver Media Group, is concerned by the happenings at the McMurdo ice station and would like you to produce an accident report detailing the events after you lost control of your hovercraft.  The accident report should include a detailed computational model that provides the projected motion of the runaway hovercraft.
-<WRAP download 35%> Code for Project 2: Part C\\ Keep them in the same directory.\\ {{:183_projects:hovercraft.py|Project 2 Code (hovercraft.py)}}\\ {{:183_projects:physutil.py|PhysUtil Module}}</WRAP>
+<WRAP download 60%> Code for Project 2: Part C\\ Keep them in the same directory.\\ {{:183_projects:hovercraft.py|Project 2 Code (hovercraft.py)}}\\ {{:183_projects:physutil.py|PhysUtil Module}}</WRAP>
+====== Code ======
+<code python>
+#Objects
+hovercraft = sphere(pos=vector(-200,400,0), radius=1)
+#Parameters and Initial Conditions
+g = vector(0,-9.81,0)
+hovercraftm = 1500
+hovercraftv = vector(53.64,0,0)
+hovercraftp = runawaycraftm*runawaycraftv
+#Time and time step
+t=0
+tf=10
+dt = 0.01
+#MotionMap/Graph
+hovercraftMotionMap = MotionMap(hovercraft, tf, 5)
+#Calculation Loop
+while hovercraft.pos.x < 0:
+    Fgrav = hovercraftm*g
+    Fground = -Fgrav
+    Fnet = Fgrav + Fground
+    hovercraftp = hovercraftp + Fnet*dt
+    hovercraft.pos = hovercraft.pos + (hovercraftp/hovercraftm)*dt
+    hovercraftMotionMap.update(t, hovercraftp/hovercraftm)
+    t = t + dt
+</code>
+<WRAP tip>
+== Tutor Questions ==
+  * **Question:**  What assumptions did you make about the motion of the hovercrafts?
+  * **Expected Answer:**  That the runaway craft has a constant velocity, and the rescue craft starts from rest with a constant acceleration.
+  * **Question:**  Are these velocities and accelerations calculated from the numbers given exact?
+  * **Expected Answer:**  No, these are only average numbers, not instantaneous.  In order to get more "exact" numbers, we would need more data.
+  * **Question:**  Is the predicted position of the rescue craft a good one?
+  * **Expected Answer:**  Not really, basing the trajectory off the first 20 seconds of data is probably not the best -- but it is all we have to work with.
+  * **Questions:**  Can you draw a plot of position vs. time for both crafts?  What are the important features of this graph?
+  * **Expected Answer:**  The point where the two curves cross is when we should jump.  One should be linear, the other quadratic.
+  * **Questions:**  Can you draw a plot of velocity vs. time for both crafts?  What are the important features of this graph?
+  * **Expected Answer:**  The acceleration is the slope of each curve (constant in both cases).
+</WRAP>