Can you help me explain to a younger child why

[saraha]

Why when you throw a peanut up into the air, it doesn’t hit the back of the plane?

I told him I would get back to him on that. 😉😆

[Catwoman]

He's going to have to throw a lot harder than that. 😉 

[Beth S]

While the child is sitting in the plane, the peanut in his hand is actually traveling at a very high speed already.
So that inertia continues when he throws it vertically while in the plane.

(Quick explanation)

Edited Wednesday at 06:26 PM by Beth S

[prairiewindmomma]

He has to fight against the force holding all of us stuck onto the earth—gravity. He isnt throwing hard enough to overcome gravity long enough for the peanut to hit the plane. (You can explain force by having him throw hard and having him throw softly. When he throws hard the peanut should go farther.)

This is why we use machines to hit planes with things like missiles. The machine is strong enough to overcome gravity to launch stuff to hit planes. We can use math to actually figure out how much force we need to be able to hit a plane with a peanut. 
 

Try to work in the vocabulary for mass, velocity, distance, etc. He’ll come back to that again in physics. 

[Miss Tick]

Wait, is he in the plane or on the ground? Beth and I assumed in the plane, Cat and prairie assumed on the ground. Either way, you've probably got the basic answer!

[prairiewindmomma]

In the plane, you, the plane and the peanut are all traveling at the same speed already…otherwise you could get to your destination before the plane, or the plane there before you. It’s the same as if you are throwing it on earth, mostly. He’s just tossing it behind him to hit the back of the plane. He still isnt throwing hard enough to hit the back of the plane to overcome gravity. A baseball player could probably throw with enough force from the front of the plane to hit the back.

[Innisfree]

If he’s in the plane, tossing the peanut up into the air, not towards the back of the plane, it’s just going to go up and come down as if he were standing in his yard at home, because the air he’s tossing it into is already moving forward at the same speed as the plane. The peanut is too.

[Innisfree]

Actually… it’s exactly as if he were standing in his yard at home… because it’s moving too, as is the whole Earth.

[prairiewindmomma]

PS—if this is your kid, ime, be prepared for a lot more of these questions. Track down YouTube videos and be prepared to show math formulas because you’ve got a kid with engineer thinking. He’s wrestling with big ideas and odds are he will see through the simplicity of your explanation. 

[prairiewindmomma]

2 minutes ago, Innisfree said:

Actually… it’s exactly as if he were standing in his yard at home… because it’s moving too, as is the whole Earth.

Not sure at what altitude gravity becomes lighter, which is why I hedged my answer. I have learned to speak in generalities with my kids…most are all now into some form of engineering and it’s this little stuff that’s relevant that if I mess up I get lovingly trolled over when they discover the bigger math behind it.

[Innisfree]

2 minutes ago, prairiewindmomma said:

Not sure at what altitude gravity becomes lighter, which is why I hedged my answer. I have learned to speak in generalities with my kids…most are all now into some form of engineering and it’s this little stuff that’s relevant that if I mess up I get lovingly trolled over when they discover the bigger math behind it.

And this is why I’m not an engineer! 😁 But the basic point holds, yes? Plane is moving, air in plane is moving; Earth is moving, air on Earth is moving.

[prairiewindmomma]

Apparently, according to a quick google, although they’ve standardized gravity for calculation purposes, the actual force varies more by location than by altitude because of the centrifugal force of the Earth spinning because the Earth has an equitorial bulge due to the magnetic forces at the poles….

[prairiewindmomma]

Just now, Innisfree said:

And this is why I’m not an engineer! 😁 But the basic point holds, yes? Plane is moving, air in plane is moving; Earth is moving, air on Earth is moving.

Yup. I’m with you….non-engineer living with a bunch of engineer people. My artistic kid and I just make eye contact in these moments at the dining room table while the engineers hash it out.

[Junie]

With questions like this, I have always told my kids something like, "I don't know how to explain it to you."

Yes, that's the easy way out. :)

[bolt.]

How young of a child?

Are we asking about someone in the plane tossing a peanut? Or someone on the ground tossing a peanut?

The youngest I can go off the top of my head is:

- On a plane, the plane shares its speed with everything it carries. When the plane isn't moving, nothing inside is moving, but as the plane gets faster everything inside gets faster because the plane shares its speed with everything it carries. You get faster, the seats get faster, the peanut gets faster. Everything inside the plane gets faster and faster all together in a group, so the group of you, your seat, and your peanut all feel like they aren't really moving because they are moving together in a group. So, the peanut, when it is in your hand, is sharing your speed, and it's sharing the plane's speed. And when you toss it, it is still sharing speed with all the other things, so it stays near your hand. It doesn't go backward because nothing makes it want to go backward. It doesn't slow down because the plane keeps on sharing its speed with the peanut.

- On the ground: Everything in the whole universe is following secret invisible rules all the time. Those rules are called physics. One of the rules of physics is called gravity. Gravity means that there is a direction called down which happens when small things like people are near or on a big thing like a planet. The middle of the planet is 'down' and all the little things feel pulled towards the planet's middle. Thankfully the planet's surface is right here. It's called the ground. The pull of gravity is why we stick to the ground. It's why it takes some effort or work to lift things up, but they fall down with no work at all. When you do the work to lift or throw something upwards, it's going to go up for a little while -- or maybe a long time, if you are very strong! But, pretty soon the work you did to throw it up there runs out, and the pull of gravity takes over. That's why the peanut, no matter how hard you throw it at a plane, can't ever hit the plane. The plane is so far away that even your strongest throw doesn't have enough force to go that high up before gravity takes over and pulls it back down. Planes are usually very far away when you see them in the sky, but at the airport planes are on the ground. You could throw peanuts at them on the ground pretty easily because they aren't so far away. But you can't actually do that because it's illegal and you could damage the plane!

[regentrude]

I want to comment on the comments - not provide an explanation for the little kid.
This is actually a pretty complicated question, because whether the ball lands in your hand or not depends on whether the plane is moving with constant velocity relative to the earth (i.e. at cruising altitude), or is accelerating relative to the surface of the earth (for example, speeding up on a level runway to gain take-off speed.)

If you are at cruising altitude, flying level and at constant speed, if you throw a ball straight up, it will indeed come back to your hand because ball and you have the same horizontal speed, the one of the plane, as pointed out by pervious posters.

However, if you throw the ball vertically upwards in an accelerating plane, it will not land back in your hand, but indeed appears to be moving towards the back of the plane during its time in the air. (In physics, we call this accelerating plane a non-inertial reference frame). I say appears to be moving backwards, because to an observer outside the plane, the ball would want to continue with the original horizontal speed it had in your hand (as per Newton's Law of Inertia), and the plane is speeding up around the ball. However, since Newton's Laws "break" in an accelerating reference frame (mathematically, additional pseudoforces appear), to you it will look like the ball is moving backwards, even though there is no backwards force acting on it.

Edited Thursday at 12:16 AM by regentrude

[saraha]

You guys rock! Thank you!!!

[Clarita]

I think you definitely need to take that child on various types of transportation and explore what happens 😋. 

I think that would be great fun.

[Cecropia]

5 hours ago, prairiewindmomma said:

PS—if this is your kid, ime, be prepared for a lot more of these questions. Track down YouTube videos and be prepared to show math formulas because you’ve got a kid with engineer thinking. He’s wrestling with big ideas and odds are he will see through the simplicity of your explanation. 

The OP might as well start stocking up on Randall Munroe books for the future...

Here's a video he might like.

https://www.youtube.com/watch?v=LWGJA9i18Co

[EKS]

You know how when you're sitting in a plane that most of the time it feels like you're sitting still?  It feels that way to the peanut as well.  This is because you, the peanut, and the plane are all going the same speed.  So when you throw the peanut up in the air, it continues to move with the plane.

[wisdomandtreasures]

Me reading these responses (go to 1:29)

[maize]

For the same reason that if he jumps into the air he doesn't hit the back of the plane.

He and the peanut and even the air inside the plane are already moving as fast as the plane and inertia keeps them moving at that speed for the short time they are in the air.

[EKS]

6 minutes ago, maize said:

For the same reason that if he jumps into the air he doesn't hit the back of the plane.

Except that he might think that is exactly what happens.

[Familia]

13 hours ago, Cecropia said:

The OP might as well start stocking up on Randall Munroe books for the future...

Here's a video he might like.

https://www.youtube.com/watch?v=LWGJA9i18Co

Thanks, got 5 people checked off my Christmas list now due to these books!!