PHYSICS MOBILE PROJECT – Forces in rotational equilibrium
OBJECTIVE:
Design and construct an art mobile around a general theme using physics to
calculate the mobile's rotational equilibrium (equal torques on each side of
balancing arm).
DIRECTIONS
1. Design a hanging mobile having a minimum of four 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 as horizontal arms.
3. Sketch the general plan of your mobile in your interactive notebook.
(Each group member should have a sketch)
4. Begin to construct your actual mobile. You are likely to achieve the best
results by starting with the lowest level and working upward.
5. Create a data table in your notebook. As you construct the element for
one side of the arm, find the mass of the element in the mobile and
record in your data sheet.
6. Measure the distance from the pivot point for the first element. Use the
torque formula to determine the distance(s) of support strings for
additional elements on the same arm and record in your data sheet. The goal is to have the torques of each arm
balanced so there is no vertical rotation. Torque calculations should be in each group member’s notebook and will be
checked as you are constructing.
7. Continue to construct the mobile following your general plan. Record the mass, distance, and torques on your data
table.
8. On graph paper make a drawn-to-scale “blueprint” of your mobile in the form of a diagram indicating the actual
lengths and masses (in SI units), positions of all strings, pivots and elements with the torques clearly labeled.
9. Hang your mobile from the ceiling in the classroom by the specified date.
10. Hand in your “blueprint” when you hang your mobile.
HINTS
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Use objects of moderate mass.
Do not use fragile or expensive objects. Handmade objects are acceptable.
Make the mobile simple, but “visually strong”.
Vary the distances of the objects to pivot points
Be creative. Use a theme you like!
Plan ahead! Calculate carefully and accurately.
MOBILE PROJECT ASSESSMENT
Names _______________________________________
Due _______________________
Blueprint should include the following:
- Name of the mobile
- Group members
- Neat, properly labeled and to scale.
- Masses of each element (remember, some objects will be added in twice or more)
- Matching distances of each element
- Corresponding torques listed
Construction
(8pts)
4
3
- Neat construction and
assembly.
- Well balanced.
- Minimum 4 arms & five
objects
- Neat construction
and assembly.
- Balanced.
- Minimum 3 arms
& five objects
2
- Mostly neat
-Some stray line or
loose knots
-Slight tilts on some
arms
-Minimum 3 arms
and 4 objects
Artistic Appeal - Makes a strong visual
- Makes a visual
- Variety of objects
and Design
impact using variety of
impact using variety used
(4 pts)
objects.
of objects.
- One or more arms
- Uses a variety of
- None of the arms
has support string
distances on each arm
have the support
at the center
- Interesting, original and string in the middle - Theme is not clear
consistent theme.
- Theme is evident
/ mobile lacks
in mobile
artistic unity
Blueprint
- includes all elements
-Includes all
-lacks an element
(8 pts)
listed above
elements above
above
-neat and very clearly
- mostly neat and
-messiness detracts
labeled
labeled
from reading and
-calculations are correct - most calculations
understanding
and match actual mobile are correct and
-several calculations
match mobile
are incorrect or do
not match mobile
20 points
Total:
possible
1
-Messines detracts
from mobile
- Tilted arms
-Less than 3 arms or
4 objects.
- Objects are all
similar, not varied
- Arms are
supported at center
-Aesthetics not
considered in
construction
-lacks more than
one element listed
above
-messy and difficult
to read
-most calculations
are incorrect or do
not match mobile
In addition to the mobile and blueprint, individual notebooks will be checked for entries as part of the
mobile process.
Interactive notebook:
- Includes drafts and initial sketches
- Calculations:
- Comprehensive, neat, accurate and easy-to-follow.
- Shows all your work including conditions for equilibrium (equal torques on opposite sides of
same horizontal arm) and the solved equations.
- Calculations match real mobile