## Submersibles

2019 Clarifications

1. (1) Based on the rule, "No teams will test their submersible in the container at any time." When the time comes, how much time a team will have to place their diver and make the final adjustment? (2) If there is enough time and material, can a team build more than one submersible and pick the best one at the diver placement time?

- 1. This is a 60 minute event. The written test is about 10 minutes long. The amount of teams in the room for a session will determine the time limit to place the diver in the container. There may be no final adjustments after the first team places their diver in the container.
- 2. There will not be an unlimited supply of materials; All teams will receive the same amount. What they create with those materials is their choice.

2. They have mentioned that the team has to show 5 experiments. Would those 5 “tries” be performed in front of the judge?

- No. These tests must occur before the competition.

3. In the 5 experiments, do we just change the weight and structure of the Cartesian structure and check if it is neutral buoyant

- How the students change their diver during the experimentation and what data they feel is importatnt to bring to the competition is totally their decision.

4. 1.Do we have to use all the materials provided for building the Cartesian diver? 2. Can the reference line be anywhere on the Cartesian diver?

- No you do not have to use all of the materials.
- Yes the reference line may be anywhere on the diver.

5. 1. saline solution - 1%-10% by weight or by volume. 2. Opening size of container, how small, big can the diver be? 3. Does diver need to be fully submersed to be considered, what if part of diver stays above surface in container.

- 1. How to Make Weight Percent (Wt%) Solutions

In weight percent solutions, the weight of the solute is divided by the weight of the solution (solute + water) and multiplied by 100. Since the density of water is 1 g/ml, the formula to calculate the amount of solute that must be mixed for a weight percent solution is:

- grams of solute = (wt% solution) x (ml of water) ÷ (100 – wt% solution)

As an example, to make 100 ml of 10% NaCl (table salt) solution, use the previous formula to find out how much NaCl you need:

- grams of NaCl = (10) x (100) ÷ (100 – 10) = 11.1 g
- 2. The container has a 7.62 cm opening.
- 3. Yes the diver must fully submerge.

6. Will the student have opportunities to test their diver before final measurement by event s How much time will the team be given to build their divers? reference point on their submersibles is this the midway point of their diver, how will the reference point be determined?

- 1. No.
- 2. See Clarification #1
- 3. The students may choose their own reference point.

7. About the "one sheet of paper with any information the team wants to use during the competition," can the one sheet paper be double-sided?

- The sheet may be double sided.