Why You Don't Fly Backward When Jumping Inside a KTX Train [Reading Science]

Why don't you fly backward when you jump inside a high-speed train?
Photo by YouTube Screenshot

[Asia Economy Reporter Kim Jong-hwa] Even if you jump inside a KTX high-speed train running at 300 km/h, you will not be thrown backward. The same applies when you jump inside a bus or subway; the passengers remain safe. Why is that?

Some people argue that since the KTX is running forward at a very high speed, if a person jumps, they should be suspended in the air and stationary, thus colliding with the rear of the train. Could someone with no scientific knowledge think this way?

What actually happens when you jump inside a moving train or bus? You land right back where you jumped. This is due to the "law of inertia," which is Newton's first law of motion stating that an object will continue moving at a constant velocity unless acted upon by an external force.

Simply put, passengers inside a high-speed train or bus appear to be stationary but are actually moving at the same speed as the train or bus. Therefore, even if you jump inside a train running at 300 km/h, you effectively jump in place.

When you are on a bus traveling at 100 km/h and look out the window at a neighboring vehicle, it appears stationary. This is because both vehicles are moving at the same speed. However, if external forces such as friction, air resistance, or gravity act, the situation can change. For example, if you jump on the roof of a high-speed train as seen in a movie scene, strong wind (air resistance) could push you backward.

Expanding the scope, the principle that you do not get thrown backward when jumping inside a high-speed train is the same reason humanity does not get flung off the Earth into space.

Although it feels like we are spinning in place every day, the Earth's rotational speed is incredibly fast. The Earth's rotation speed is 463 meters per second, or 1,667 km/h, comparable to the speed of a supersonic jet.

The Earth is like a massive spaceship carrying 7 billion people, flying at a speed of 30 km per second.
[Photo by YouTube screenshot]

The Earth's orbital speed around the Sun, which takes one year to complete, is even faster. The Earth's orbital speed is 29.8 km per second, or 107,000 km/h, which is about 87 times the speed of sound. This is similar to the speed of a spacecraft traveling 30 km per second.

It is an astonishing speed. Even though the Earth is rapidly flying through space and centrifugal force is acting, not a single person is flung off the planet. This is because people move at the same speed as the Earth.

Many cars and trains move swiftly on Earth, but their speeds are insignificant compared to the speed at which the Earth?a massive spaceship carrying 7 billion people?flies around the Sun at 30 km per second while rotating daily at 1,667 km/h around its axis.