Item Description: This event asks students to answer questions and make a scale model of some of the planets based on a table of planetary distances. Questions 1 and 3 can be answered with little background knowledge. Students will have to know how to make a scale. Question 2 requires students to have some background knowledge about how the planets move and the space in between them. Question 3 asks students to recognize that planets which move more slowly and have farther to go will take longer to travel around the Sun. This is a logical conclusion from the information given. Question 2 is more difficult because students need previous knowledge. Straight line motion to a planet directly between Earth and the sun would be impractical for several reasons. Most importantly both planets would be moving perpendicular to the line between them. Thus a ship leaving the Earth would have a large amount of momentum in the wrong direction. That momentum would have to be overcome before travel could start. This would take a large amount of energy. Then you must travel in a straight line in starting at zero speed. Once you get to Venus' orbital distance you might stop and notice that there wasn't a planet there. In the time you took to get there, the planet moved in its orbit. Even if you timed it to get there early, Venus is moving at more than 40 km/sec. A head-on collision with a planet moving at 40 km per second would be very hazardous to your health. The best orbit is one which moves with the planets. The spaceship can use the momentum of Earth's orbit to get to Venus. By slowing down slightly, the ship would go into an elliptical orbit with the closest point of the orbit being at Venus' distance to the Sun. This event will be scored on a 22 point scale. That number will then be converted to the standard 4 point scale. A conversion chart is below. Total Points Center 0 - 2 0 3 - 7 1 8 - 12 2 13 - 18 3 19 - 22 4 ME128 Rubric Question 1 (worth 12 points) The student receives 2 points for each of the 5 planets drawn to a relative scale and labeled. If ANY planets are drawn and labeled, then the student receives at least two points because one planet will serve to define the scale. A rubber band with a scale of the planets marked on it can be used as it can stretch to fit most scales. If two planets are to scale, the following formula should be an equality. Scale Distance Planet 1 Scale Distance Planet 2 = Real Distance 1 Real Distance 2 There are ten combinations which would normally have to be done, however, if Mars agrees with Earth and Mars agrees with Jupiter then Earth and Jupiter are to scale. It is important to try different planets to match because if only one planet is off and it is the only one you use as your basis of comparison you would get 2 points instead of 8. Also, some students will make their scales too large so Pluto won't fit. This is acceptable if the students list the position the planet would have on a longer ruler. An additional 2 points will be given if students have written a scale which agrees with at least 4 of the planets. The scale will probably have 1 cm=x km, but if the student uses 1 in. or mm instead of 1 cm. this is acceptable. Also, if the student has the wrong order of magnitude (i.e. 1 cm=15 Km instead of 1 cm=15x107 km) they can still receive one of the two points. The scale must be written and at least 4 planets must match it to receive two points. Question 2 (4 points) (a) Student receives two points for giving a basically correct answer and (b) two points for explaining their answer. (a) (2pts.) Any of the following are acceptable: 1) Because the planets are moving. 2) By the time you get there it won't be there. 3) It takes too much fuel. 4) An intersecting (tangential) orbit is better. 5) It would be moving sideways. There are three main points here which are listed in the item description. (b) (2pts.) The following is correct and helpful information which justifies the answer above. (b) (1) & (2) If you set your path on where it is and then start, Venus will have orbited some around the Sun so you would miss it. (3) You would have to stop your motion and move in and then move sideways again. (5) Once you got there it would be moving sideways. You would collide at high speed. (4) You let the Sun do the work of pulling you around and when you got there you would be going the same speed, and the right angle. OR Student can receive 1 of 4 points for one of the following: 1) You might get hit by an asteroid or meteor. (A planet is not acceptable) 2) There might be stuff in the way. 3) The gravity might pull you in. 4) You might miss. Without further explanation these ideas could apply to any trip from Earth to Venus, not just a straight line trip. Question 3 (6 points; A, 4 points - B, 2 points) (A1) (+1) The student states that Pluto has the longest year or they can say "the farthest planet has the longest year" as long as no other planet is named. (A2) (+1) The student explains reason for (A1), for instance: "It has the farthest to move." "It is the farthest from the sun." "It moves the slowest." (A3) (+1) The student states that Mercury has the shortest year or they can write "the closest planet has the shortest year" as long as no other planet is named. (A4) (+1) The student gets (A3) right and explains the reason for (A3), for instance. "It has the smallest distance to move." "It is the closest to the sun." "It moves the fastest." (B1) (+1) Student responds with Venus. (+1) Because it is closest to us.