SUMMARY: How is it that cats are able to jump down from high places and not hurt themselves? Researchers in this study observed 5 cats, jumping from various heights, for clues as to what sorts of forces and shock absorbers were at work. The results showed that cats used their front legs to absorb a certain amount of energy from a fall. However, with increasing height, cats started to use their hind legs to absorb the extra energy. The study looked at ground reaction force, angle and angular velocity of all the joints in a cat’s limbs, joint movement, joint moments (torque), joint power, and energy of the fall.
LESSON COMMENTS: This is a great article for a physics class learning about forces, motion, and energy. It could also work for an interdisciplinary class looking to find a connection between biology and physics. Also, who doesn’t love cats? Teachers can introduce this article by showing students some videos of cats jumping from high places. Topics that students will need to be familiar with include: force, net force, reaction force, torque, velocity, angular velocity, biarticular joints, muscle and joint groups, and energy. Yes, biology (specifically anatomy and physiology) and physics are closely tied together in this experiment. Personally, I would start with Figure 8, since it illustrates the results in the clearest way. It shows the energy distribution in the fore and hind limbs as the cats jumped off of higher and higher places. Fig 1, 4-7 are best analyzed with help from the teacher. These figures show various forces at work, in both fore and hind limbs, during the landing.
Wu, X., Pei, B., Pei, Y., Wu, N., Zhou, K., Hao, Y., & Wang, W. (2019). Contributions of Limb Joints to Energy Absorption during Landing in Cats. Applied bionics and biomechanics, 2019, 3815612. doi:10.1155/2019/3815612