Feb 212013

You only have control of the platform height. In general, you do not have control over the platform speed. The only instance for which you have control of the platform speed is when the platform speed is ZERO.

So instead of trying to make the speed of the platform match the speed of the spuCraft, maybe you should think about the speed of the spuCraft matching the speed of the platform.

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Feb 212013

Next, I would suggest that you make a list of the quantities in the problem that you know, and those that you want to know.

In particular, you should look at what we call the boundary conditions. Answer the following questions:

  • When the spuCraft goes through the light gate, what quantities doe you know?
  • When the spuCraft latches onto the payload, what quantity/quantities do you know?
  • When the spuCraft latches onto the payload, what quantity/quantities do you want to find?

What are the forces acting on the spuCraft between the light gate and the payload latch? Given this, how can you use Newton’s Second Law or the Work-Energy Principle to relate the boundary conditions. In particular, you need to relate the the things you want to know to the things you know.

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Feb 212013

First, I suggest that you formulate a general strategy. How are you going to get the spuCraft to latch onto the payload? As described in the video, you need to hold the payload a fixed distance from Pokey while Pokey and the payload are going at exactly the same speed.

How are you going to do that?

You may remember that the input for the Drop world was the thruster force. Do you know what the input for the Lift world is? If not, I want you to go to the spuPilot and find out what it is.

Click here when you know what the input is.

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Feb 212013

As I discussed else where (… switch to new input script?), it is necessary to switch to a new input script, defined by you, when the spuCraft passes through the light gate.

However, if you switch input scripts a half second or so after passing through the light gate, you’ll probably be fine. If you switch just a little too early, you’ll probably be fine too.

Since you do not have to make the switch at a precise time, you can use the manual switch rather than the trigger.

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Lift Help – When should I switch to new input script?

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Feb 212013

Presumably the position where you are going to place the platform is going to depend on the speed and height of the spuCraft as it passes through one or more light gates. You pilot does not know the height and speed of the spuCraft until it passes through the light gate. Therefore you shouldn’t switch to the new input script until it has passed through the light gate(s).

If you switch to the input script too early, it will start positioning the platform based on bad information. Then, when you get good information as the spuCraft passes through the light gate, the platform might be too far away to get to the right location in time.

Related question: Do I need an automatic switch?

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Feb 212013

Yea. Sometimes our equations get real long. One way to make them shorter (per equation box) is to split the equation into part and then use custom pilot functions to write some of the parts.

There is a video which provides an introduction to pilot functions. You can watch it here. The idea is rather simple. Suppose you wanted to type the following equation into an input script:

(x^2 + y^2)*h*v/sin(sqrt(x^2+y^2))

One way to split this up is to define the function pf1 [on the “Functions screen”]. In the pf1 box type:

x^2 + y^2

Then, in the input script box, instead of typing the first equation above, you can write


This is a little shorter. Perhaps you can use the same idea to shorten the equations you need to type in.

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Feb 212013

Often, the Work-Energy Principle is much quicker and easier to use than direct Newton’s second law, F = ma. However, you can’t always use Work-Energy. When asking yourself whether you can use a Work-Energy approach to solving the problem, you should ask yourself a few questions:

  1. Do the knowns and unknowns in the problem involve positions (displacements) and speeds? If so, then work-energy is a candidate. In contrast, time is not part of the work-energy principle. If your problem requires you to determine time, or to know time information, then work-energy is not for you.
  2. Are all the forces which do work ones for which we have simple expressions for work (i.e. constant forces, gravity, and spring forces)?

If both of these are true, then your problem might be a good candidate for a work-energy approach.

If you want to see an example (not Lift, something simpler) of Work-Energy and F=ma applied to the same problem, outlining strengths and weaknesses of both approaches, I encourage you to watch the video below.

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Feb 072013

Well, there’s a reason this is called the “Prodigy” level. You have to be particularly talented in order to solve it. If you’re talented, you should be able to figure it out yourself.

However, I will tell you that you probably shouldn’t spend too much time trying to solve this until you complete the Free Fall Challenge. After Free Fall the approach for completing Drop Prodigy should be more clear.