Why is it easier to balance on a plane than a bus, even though it is going at a faster speed?


This probably sounds stupid, but why is it easy to get up in a plane, and walk around as if you were on the ground. Then on a bus it’s harder even though the speed of the vehicle, is slower?

In: Physics

The speed is irrelevant because both you and the plane/bus are moving at the same speed, so the speed relative to you is effectively 0. What’s more important about balance is the change in speed/direction during travel.

On a bus, the roads are bumpy, the suspension is soft to allow for said bumps, and there are regular starts, stops, and turns. This makes for a lot of change in speed/direction as a person tries to walk down the aisle. It’s hard to maintain balance when the environment around you is constantly changing.

On a plane for the majority of your travel the ride is very consistent. Your cruising speed and altitude don’t vary much from moment to moment (barring turbulence), so relative to yourself the plane acts as a pretty solid steady floor on which to walk around.

The primary difference is the *potential* extreme. While a bus COULD in theory get into a big time accident and flip over or suddenly decelerate from 55mph to 0 mph, a plane’s potential for change is way worse, with the option of barrel rolling multiple times in the case of catastrophic engine failure or mid-air collision, dropping hundreds of feet in a few short seconds due to radical turbulence, and in the event of a crash landing decelerating hundreds of miles per hour to 0 in an instant. It’ll be a lot harder to maintain balance during a mid-air aeronautical catastrophe than it would in a bus crash.

Inertia+Bernoulli effect=balance. Basically if a bus had Indy car type spoilers, it would have the same balance

It’s not the speed itself, but the changes in speed which matter most when you’re trying to stay upright.

A big and heavy plane doesn’t change it’s speed fast enough to cause trouble (except during for example take-off and turbulence), while a bus is constantly maneuvering around traffic on a bumpy road.

Because a plane is a constant speed, whereas a bus is braking, accelerating, etc.

As long as there’s no speed change, it feels like it’s not moving

No question is stupid.
The thing that makes it hard to get up is not the speed rather the changes in speed, i.e. ecclleration and deceleration. Buses change speed more often, slowing down and speeding up, and whenever it does so, you experience a force (not real) that feels like you are being thrown forward (deceleration) and backward (excelleration). In addition, the changes in course are more profound in buses than in air plains, these also play role in throwing you from side to side

Basically, you don’t feel constant velocity, you feel change in velocity (acceleration). The Earth is rotating at 1000mph at the equator and 67000mph around the sun, but you don’t feel it because the velocity doesn’t change. The bus is bouncing around everywhere, stopping/starting, etc.

Before we go into the differences between a bus and an airplane, let’s establish some common language:

So when your standing still, you have a *location*.

If your location changes over time (i.e., you are moving), you have a *speed*.

If your speed changes over time (e.g., you are speeding up), you are *accelerating*.

If your acceleration changes over time (e.g., you are speeding up even faster than you were before), you are experiencing *jerk*.

Next step, let’s figure out which of these are harder/easier to balance when experiencing.

Location is easy. Everybody’s somewhere and that doesn’t require balance.

Speed is also easy. All it means is that you are moving constantly. In fact, since the Earth is moving, you’re always moving even when you’re “standing still”. No problem balancing.

Acceleration, surprisingly, is also easy. For example, you’re always “falling” towards the center of the Earth, but the ground is holding you up. You basically just have a constant force against the acceleration and you’re happy.

That just leaves jerk. Jerk is where we use balance. As the acceleration changes, we have to change our counter force. (e.g., lean backwards when the bus puts it’s breaks on, pull on the overhead bar when the bus takes a turn to keep from falling over)

Ok, so now let’s think about the differences between a bus and an airplane.

At any moment the both have a location, but that doesn’t really matter.

The airplane goes much faster, but like we talked about that doesn’t matter for balance.

The airplane can accelerate rapidly, but that doesn’t matter for balance either.

Finally, which one is jerkier? Well, during takeoff and landing, the airplane. It’s rapidly changing it’s acceleration from nothing full thrust from the engines. But guess what, during that time you can’t move around or balance, because it’s dangerous and difficult. But once an airplane is cruising at altitude it’s very steady. No rapid changes to the left or right. No rapid changes in acceleration. Really, nothing except turbulence and potential emergency until you land.

The bus however is constantly experiencing jerk. Every pothole, every turn, every slow down or speed up requires you to counteract the force in order to stand still.

Finally, unlike the plane where you can frequently anticipate jerk, (i.e., when you take off or land), on the bus, you often have to react and depending on your reaction speed you’ll find yourself moving around quite a bit.