Differences

This shows you the differences between two versions of the page.

--- summer_2019:gravitation [2019/07/31 15:40]
tallpaul
+++ summer_2019:gravitation [2019/08/06 02:54]
tallpaul
@@ Line 1: / Line 1: @@
-====== Satellite Orbit Activity ======
+**Follow this link for the activity and the instructions: [[https://trinket.io/library/trinkets/4b1a7a7441|link]]**
-===== Part A (Non-Computation) =====
+You should see something that looks like this:
-{{ summer_2018:river_photo_2.jpg?400 |}}
+{{ satellite_trinket_screenshot.png?600 | trinket screenshot}}
-The Carver Media Group is planning the launch of a new communications satellite. Elliot Carver (head of Carver Media Group) is concerned about the launch. This is a $200,000,000 endeavor. In particular, he is worried about the orbital speed necessary to maintain the satellite's geostationary orbit (and if that depends on the launch mass). You were hired as an engineer on the launch team. Carver has asked that you allay his concerns.
+If you click on the "Instructions" tab in the upper right, a set of instructions for the activity should pop up. Click between "Instructions" and "Result" to alternately view the instructions and the animation. If you prefer, the same instructions are also listed below.
-<WRAP info>
+. Run the code and see what happens! You should see a satellite shooting off into space, completely unaffected by gravity.
-==== Learning Goals ====
+. Read the code, and try to understand how each line is impacting the animation. If you're not sure, try changing the line, and see what happens. Keep track of what you find by writing comments. (Use the # character.)
-  * Forces cause changes in momentum
+. Try using your physics knowledge to fix the code so that gravitational force is being applied correctly.
-  * Uniform circular motion
-  * Newtonian gravitational force
-</WRAP>
+. **Extra**: Uncomment (take away the # characters) from the chunks of code marked 'Extra'. Try to fix the graphs so that they correctly display the energy of the satellite. Try to add another curve to the graph that tracks the satellite's total energy.
-===== Part B (Computation) =====
+. **Extra Extra**: Uncomment from the chunks of code marked 'Extra Extra'. Try to use it to help you create a net force arrow that updates as the satellite moves. Now you have a living, changing, free-body diagram! Try to add another arrow that models the updating satellite momentum.
-**Follow this link for the activity and the instructions: [[https://trinket.io/library/trinkets/4b1a7a7441|link]]**
+For more information on glowscript tools, check out: [[https://www.glowscript.org/docs/GlowScriptDocs/index.html]]
-You should see something that looks like this:
+<code>
+GlowScript 2.7 VPython
-{{ satellite_trinket_screenshot.png | trinket screenshot}}
+# Window setup
+scene.width = 600
+scene.height = 400
-If you click on the "Instructions" tab in the upper right, a set of instructions for the activity should pop up. Click between "Instructions" and "Result" to alternately view the instructions and the animation. If you prefer, the same instructions are also listed below.
+# Objects
+Earth = sphere(pos=vec(0, 0, 0), radius=6.4e6, texture=textures.earth)
+Satellite = sphere(pos=vec(7 * Earth.radius, 0, 0), radius=1e6, color=color.red, make_trail=True)
-. Run the code (click "Run") and see what happens! You should see a satellite shooting off into space, completely unaffected by gravity.
+# Parameters and Initial Conditions
+G = 6.7e-11
+mEarth = 6e24
+mSatellite = 20
+pSatellite = vector(0, 50000, 0)
-. Read the code, and try to understand how each line is impacting the animation. If you're not sure, try changing the line, and see what happens. Keep track of what you find by writing comments. (Use the # character.)
+# Time and time step
+t = 0
+tFinal = 1 * 60 * 60 * 24     # 1 day
+dt = 1
-. Try using your physics knowledge to fix the code so that gravitational force is being applied correctly.
+############################# Extra ##############################
+## energyGraph = graph(xtitle='time (s)', ytitle='energy (J)')  ##
+## kineticGraph = gcurve(color=color.green, label='kinetic')    ##
+## potentialGraph = gcurve(color=color.blue, label='potential') ##
+##################################################################
-. **Extra**: Uncomment (take away the # characters) from the chunks of code marked 'Extra'. Try to fix the graphs so that they correctly display the energy of the satellite. Try to add another curve to the graph that tracks the satellite's total energy.
-. **Extra Extra**: Uncomment from the chunks of code marked 'Extra Extra'. Try to use it to help you create a net force arrow that updates as the satellite moves. Now you have a living, changing, free-body diagram! Try to add another arrow that models the updating satellite momentum.
+################################# Extra Extra ###################################
+## FnetArrow = arrow(pos=Satellite.pos, axis=vec(0, 0, 0), color=color.yellow) ##
+#################################################################################
-For more information on glowscript tools, check out: [[https://www.glowscript.org/docs/GlowScriptDocs/index.html]]
+# Calculation Loop
+while t < tFinal:
+    rate(10000)
+    Fnet = vec(0, 0, 0)
+    pSatellite = pSatellite + Fnet * dt
+    Satellite.pos = Satellite.pos + (pSatellite / mSatellite) * dt
+    t = t + dt
+    ############ Extra ############
+    ## kineticGraph.plot(t, 0)   ##
+    ## potentialGraph.plot(t, 0) ##
+    ###############################
+    ########### Extra Extra ###########
+    ## FnetArrow.pos = vec(0, 0, 0)  ##
+    ## FnetArrow.axis = vec(0, 0, 0) ##
+    ###################################
+    # Earth Rotation (just for fun!)
+    theta = 2 * pi * dt / tFinal
+    Earth.rotate(angle=theta, axis=vec(0, 1, 0), origin=Earth.pos)
+</code>