Can you catch a cat … or not?

We all love cats! The internet is filled with goofy videos of those soft little adorable fur balls. And they seem quite fun to play with. However, imagine you brought a cat home, but it didn’t like you and wanted to run away. Could you catch it?

All the scientific observations point towards the answer: No, you can’t run faster than the average cat! Seems quite surprising, right? Sure they are agile, athletic, and can fall from buildings several floors high and survive. But surely you can run quite fast too, right, with your height and longer legs giving you a significant advantage? So how does science explain the ability of a small animal like a cat—weighing just 5 kgs and less than a foot in height—to run faster than you?

Science behind in catching a cat

There are a few factors that we may have to consider in order to understand this. Let’s figure them out here-

Speed depends on the food

Biologist Myriam Hirt, at the German Centre for Integrative Biodiversity Research in Germany, believes that our speed depends on how quickly we can convert the food that we eat into energy through the process called metabolism. Large animals need more nutrients to power their bigger muscles, causing muscle fatigue to occur faster. Essentially, it means that their muscles run out of fuel much more quickly than smaller animals. This seems to explain why we could even outrun the mighty Tyrannosaurus Rex.

how speed of an animal changes with its weight — Figure showing the variation of speed and weight of different animals, after Hirt et al., (2017)

Speed depends on the body design

On the other hand, biomechanist Michael Gunther and his colleagues propose that our speeds can be easily explained through classical mechanics (the foundations of which are Newton’s laws of motion). They put forth a model which considers two key criteria for animals’ speeds: drag and inertia. What do these mean, and how do they affect our running?

Have you ever tried to run against the wind blowing on your face? You will notice that it becomes much harder, and your speed decreases significantly. The force that you experience is called air resistance or drag. This air resistance increases with the total surface area of your body facing the wind and depends on your body design.

This drag is why engineers design sleek race cars and aeroplanes. The designs help reduce the extra force required to counter the air resistance to go much faster. Even we can use the same principles to go fast. Here is a video of a cyclist reducing his surface area to gain speed and outsmart his competition. However, this doesn’t work while running. The way our bodies are designed, if we try to reduce our drag, our lung capacity will decrease, and we won’t be able to get enough oxygen in our body to maintain a high speed. So, we can’t really decrease our drag by much.

Inertia also has a role to play in the speed

The other thing that determines speed is inertia. Inertia is essentially the property by which bodies/ objects at rest tend to remain at rest unless acted upon by force. In the case of animals (including humans), muscles provide the force required to get them moving from a standstill. Inertia, and consequently the force required to move their bodies directly depend on their total weight. It makes sense then that the lesser their weight, the lesser energy needed to move, and the faster they can go. One point for cats! But what about us humans? How do we run faster?

What about the speed of humans?

A human’s running speed also depends on the total muscle strength. Those huge muscles you see on Farhan Akhtar in Bhaag Milkha Bhaag are not just for show! That strength helps runners push the ground with a larger force. As per Newton’s third law, the ground exerts an equal amount of force on them which they then use to propel themselves faster. Professional runners put almost five times their weight on the ground in less than one-tenth of a second! To see it in action, check out this video.

But an increase in muscle mass also means that your body needs to spend more energy to run. So the fastest runners in the world need to increase their muscle strength while also limiting their weight. That means cutting out fat as much as possible. No more late-night ice-cream trips if you want to run like a pro!

Thankfully, scientists have found the weight that is just right: around 50 kg. And no surprise here, the weight of the fastest animal on earth (Cheetah) is pretty close to this optimum weight. However, the top speed also depends on the design of the animal. Scientists predict a top speed of around 40 km/hr for a 100 kg human. Usain Bolt, the fastest human on earth, has a world record for approximately that speed!

Though, even at that mind-boggling speed, Usain Bolt would still be left in the dust by the average house cat, which can run at speeds of 50 km/hr. That has a lot to do with how cats are built, especially with four legs giving them a considerable advantage over two-legged animals such as us!

So, to answer the question we started with, no, I wouldn’t suggest running after a cat that doesn’t want to be caught. You are better off offering treats to get it to like you!

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