Static Equilibrium lab

Art Mobiles

• Final Project

Mobiles and Physics

• A mobile is an arrangement of materials that are balanced in a number of different ways. Everything is connected and can move if additional force is applied

• Translational Balance: Fnet = 0

• Rotational (torsional) Balance: Tnet = 0

Kinetic art

Alexander "Sandy" Calder (1898-1976) was an artistic pioneer who created the art form called the mobile. By the early 1970s, Calder's mobiles were famous worldwide. His sculptures ranged in size from the monumental

to jewelry-sized.

Alexander Calder’s work

Directions

1. Construct a hanging mobile having a minimum of three freely swinging horizontal arms using an artistic general theme.

2. Select the hanging items of the mobile. Plan to use wooden dowels or metal rods.

3. Sketch the general plan of your mobile. Keep this sketch and all of your work in your graph notebook. Be sure to document your procedures and modifications. This journal is to be turned in with the project.

4. Find the mass of each element in the mobile including the rods.

Directions continued5. Determine the position of each support string. Strings may not be

attached at the center of mass of a support.

6. Complete the mobile “blueprint” indicating the actual lengths, positions of all strings, pivots and elements with the forces clearly labeled.

7. Demonstrate by neat calculations that translational androtational equilibrium exists. Calculate % error of torque comparisons. List possible sources of error

8. Construct your actual mobile.

Hints

1) You are likely to achieve the best results by starting with the lowest level and working upward.

2) Use objects of moderate mass. Do not use fragile or expensive objects. Handmade objects are acceptable.

What each person or team needs to obtain

• 3-4 wire hangers (wire throughout)

• Thread

• 1 heavy plastic hanger

• 3-5 small objects (to hang)

Materials for Mobile Project

1 wood, plastic hanger

3 metal hangers

3 small irregularly shaped objects

Thread

What you will turn in for mobile project…

1) A drawing or picture of the finished mobile. Identify materials used, showing that no movement of mobile will be constricted.

2) A series of free-body diagrams for each level of the mobile, complete with masses and distances to pivot points

3) Calculations that show the % error for each level of mobile when comparing generated clockwise and counterclockwise amounts. Show all set ups for calculations

Value of finished project

• Completed mobile (satisfies conditions: 1 level with 4 things hanging down, a 2nd level that has only one object hanging down)

• Up to 30 points

• Free body diagrams showing mobile balanced and hung• Up to 15 points

• Mathematical derivation of % error for each level. • Up to 15 points