[ Watch the Video: Water Experiment 1: Empty In The Same Time Span ]
Gerard LeBlond for redOrbit.com – Your Universe Online
A recent study from the Georgia Institute of Technology on how quickly animals urinate reveals that previous information on urinary flow dynamics may not “hold water” after all.
David Hu, Georgia Tech’s assistant professor led the study of how quickly 32 different animals urinated. The findings indicate that animals will urinate in about the same time no matter how large their bladders are. For instance, a cat’s bladder holds about .17 ounces of urine, while an elephant’s bladder holds about 609 ounces. However, both will take about 20 seconds to empty their bladder. The research also revealed that all animals that weigh more than 6.6 pounds take about the same time to urinate.
“It’s possible because larger animals have longer urethras. The weight of the fluid in the urethra is pushing the fluid out. And because the urethra is long, flow rate is increased,” David stated.
According to the researchers, gravity has an impact on how fast the urine flows on animals. Larger animals have longer urethras allowing them to empty their bladders in jets. An elephant’s urethra is about 3.5 feet long that allows it to urinate at about 13 feet per second. Smaller animals’ urination has a minimal effect from gravity.
“If its urethra were shorter, the elephant would urinate for a longer time and be more susceptible to predators,” Hu explained.
Patricia Yang, a graduate student that was part of the research team, explained that smaller animals “urinate in small drops because of high viscous and capillary forces. It’s like peeing in space. Mice and rats go in less than two seconds. Bats are done in a fraction of a second.”
The research team observed 16 animals from the zoo urinating, then watched cows, horses, dogs and other animals on YouTube videos relieve themselves. As they watched, the team realized that their findings could help engineers design products.
“It turns out that you don’t need external pressure to get rid of fluids quickly. Nature has designed a way to use gravity instead of wasting the animal’s energy,” Hu said.
The manufacturing of water tanks, backpacks and fire hoses could benefit from their research and be manufactured more efficiently. The team has demonstrated in an experiment that uses a tea cup, a quart and gallon containers of water, empties in the same duration of time using different lengths of connected tubes. A second experiment uses three cups filled with the same amount of water using different length tubes — the longer tubes attached to the cup emptied faster.
“Nature has shown us that no matter how big the fire truck, water can still come out in the same time as a tiny truck,” Hu added.
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