What is it about?
A can sliding on a table, or a planetary lander moving horizontally across a surface, strike and stick to a low obstacle. Will they rock back to upright, or tip over? We show how the tip-over speed depends on the object's shape, and local gravity.
Featured Image
Photo by Brian McGowan on Unsplash
Why is it important?
In early 2024 two lunar landers (SLIM and IM-1) toppled over on landing. Although other effects turned out to be the culprits for these landers, their "top-heavy" designs did not help! We show how to calculate the tip-over speed of any object on any planet. This problem is a practical example of angular momentum conservation in an inelastic collision. and suggest how to test our results with a simple experiments in the physics teaching laboratory. A video abstract is provided at the journal website.
Perspectives
Physics textbooks typically only provide a couple of examples inelastic ("sticky") collisions that conserve angular momentum: One disk dropping onto another, and a falling rod that catches on a pivot. Both are somewhat contrived. The landing mishaps of SLIM and IM-1 prompted us to look into this problem, and the calculation of tip-over speed ended up as a practical -and accessible - demonstration of the same physics principles. It also lends itself to testing in the teaching laboratory using easy-to-assemble equipment. Supplementary materials provide more details on the collision physics and the lab experiment. A video abstract showing the experiment is provided at the Physics Education journal website.
Dr. Philip Blanco
Grossmont College
Read the Original
This page is a summary of: Tripping on the Moon, Physics Education, June 2024, Institute of Physics Publishing,
DOI: 10.1088/1361-6552/ad539c.
You can read the full text:
Resources
Supplementary information
A PDF containing additional information, and a simulation file for use with the Algodoo physics simulation.
Tripping on the Moon - open access (US government)
Since my co-author is a US government employee, he is authorized to publish the paper on his website. This is a direct link to the PDF. See also the supplementary materials.
Contributors
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