|
For reference, the introduction is here.
Part B. The Challenge
The situation is shown in the photo to the
right. Click on this link to open a larger version of the photograph in a new window. Print the photo.
Given: Two spring scales hang from a horizontal rod. A ball painted red hangs from both scales, and the system is in equilibrium. Except for the paint on the surface of the ball, the ball is composed of a single element. Forces in newtons can be read directly from the scales to the nearest 0.1 N. The diameter of either scale is 0.2406 m.
Goals:
- Determine the density of the red ball to 3 significant figures.
- State the element of which the red ball is most likely composed. Cite your source for the density of the element.
Tools you'll need: Centimeter ruler, protractor, print of the photo
About working with a partner:
- You'll work with an assigned partner or partners to design a method of solution.
- Each person in the group will take their own measurements and write their own solution for submission.
- Partners may compare their results before submitting their solutions.
Requirements:
Show your work leading up to your completion of the goals. Clarity of expression in words, mathematics, and diagrams are particularly important, since the design of your product (the report) and the experiment are largely up to you. Include at least the following.
- As you would for a lab, state title, goals, your name, and partners' names.
- Your method must show good use of the physics appropriate to the situation. Provide a description of your method.
- Draw a quarter-page diagram of the forces, and label them for reference.
- Clearly show on the photo the coordinate axes. We recommend that you select the line of action of one of the forces as the +x-axis. That force will then have a direction of angle of 0°, simplifying the calculations of components. (There is no requirement that the +x axis be horizontal.)
- Measure to appropriate precision and accuracy, and present your measurements clearly. Report all direction angles according to convention: counterclockwise from whatever line you designate as the +x-axis.
- Cite your source for the density of the element.
What to submit:
Submit a scanned pdf of 1) your solution and 2) the photo showing the coordinate system and any annotations. Name the file L120B-lastnamefirstinitial.pdf.