If you fall and skid to a stop on a carpeted floor, you can get a rug burn. Much of this discomfort comes from abrasion, but there can also be a real burn where the skin was too hot. When running, your body has energy.
When you fall, the friction between the carpet and your body transforms your initial energy into energy.
Because the surfaces in contact (your knees and the carpet) are heating up, it can result in a burn.

Aproduction line at v. j. sugumaran's machine shop has three stations. the first station can process a unit in 7 minutes. the second station has two identical machines, each of which can process a unit in 16 minutes (each unit only needs to be processed on one of the two machines). the third station can process a unit in 10 minutes. ▼ is the bottleneck station, with a bottleneck time of nothing minutes per unit (enter your response as a whole number).