1556 Woodland Dr | Saline, MI 48176 | T: (800) 367-6695 | www.arborsci.com
©2020 Arbor Scientific All Rights Reserved
Stretching the Lycra
It is important to create an even tension across the sheet; this is best
achieved by methodically working around the whole sheet attaching
opposite points in pairs as per the diagram to the right.
Once the first eight clips are in place the remaining eight should be
spaced evenly between them. The sheet should then only require
small adjustments to achieve a smooth even stretch across the frame.
1. Star Formation: Start by rolling two or three small marbles in random directions across the
sheet. Notice that the force of attraction between them is small as the distortion that they
create in the sheet is small. As more marbles are added to the sheet one or two will touch and
create a larger dimple. This will continue until the dimple is large enough to create an
appreciable depression and any marbles that are added to the sheet will be attracted
immediately to the group.
2. Orbital period: Place the large metal ball in the center of the sheet to represent a star. Roll a
marble in such a way
that it ‘orbits’ the star. As the marble begins to get closer to the large
metal ball add a second marble. The variation in orbital period with distance should be
apparent. Extra marbles may be added as required.
3. Variation of force with mass: If the large metal ball is replaced with a heavier object
–
maximum 2kg. (Stock masses work well for this) A more massive object creates a larger
dimple and therefore other masses are attracted to it with a greater force
4. Earth and moon pair: By selecting two flat masses (roughly 500g) and placing them some
distance apart on the sheet. It is possible to model the ‘free return’ trajectory of a craft that
would loop the moon and return to Earth.
•
Remove the sheet and fold and l
ift off the ring to disassemble the lower structure.
•
Hold the ring vertically with one side on the ground, hold firmly at a joint and remove a bolt with
a ball knob. Pull the joint apart and carefully lower one end to the ground. It can be helpful to
stand on the tube and ‘walk’ it open.
Do not allow the ring to ‘spring’ apart.
•
Once the tension is removed the remaining ball knobs and bolts may be removed. Leave the
nylock nuts and bolts in place.
Introduction video:
Reviewing Newton’s Laws Coolstuff Blog:
https://www.arborsci.com/blogs/cool/oct-newton-s-laws-revisited
Activities
Disassembly
Resources
