# Weight of a plane

1. Sep 22, 2007

### genneth

A large passenger jet is standing on a runway. You have a toolbox, filled with some typical tools -- perhaps one that could be used to repair a bike or a car or something. How do you find the weight of the plane?

2. Sep 22, 2007

### neutrino

I'll look it up. (Meaning I'll find the mass from the handbook.) :tongue2:

3. Sep 22, 2007

### genneth

My personal favourites (though apparently not correct, who knows why ):

- Throw a spanner past the plane and measure the deviation due to gravitational attraction
- Throw the whole toolbox at the plane hard enough for it to go through and lodge in the plane somewhere, and measure the recoil of the plane.

4. Sep 22, 2007

### neutrino

You know, if the toolbox has a torch, we could shine light from behind the plane and measure the deviation of flash light. (Hmm...I wonder if it's Flash light or Flash-light...).

5. Sep 22, 2007

### genneth

Or the acceleration due to photon pressure... People never seem to believe me when I say my eyesight and sense of timing is that good. So cynical...

6. Sep 22, 2007

### arildno

In my typic toolbox, I always carry with me the technical specification sheet for the plane I'm about to board.

I'd check that one out first.

7. Sep 22, 2007

### Jimmy Snyder

I heard this one before. First you weigh the plane with the toolbox on board, then you weigh the toolbox. The weight of the plane is the difference.

8. Sep 22, 2007

### Cyrus

Err, couldnt you just weight the airplane w/o the tool box? What would be the point of taking the difference?

9. Sep 22, 2007

### genneth

What's that...? Sounds like a plane flying overhead...

10. Sep 22, 2007

### neutrino

I'll find the force on the Earth due to the plane.

I suspect someone will read all the posts in this thread and make up a story (and eventually electronic spam) about how a famous scientist, when he was young (I'm sure it will be a 'he'), gave all these answers for the question "How do you weigh a flying plane with a toolbox?" and was failed in the exam just because he didn't give the "correct" answer.

Hey, I've posted approximately $1000\sqrt{3}$ posts! And 3 non-GD posts ago I would have had a Ramanujan Number of posts.

Last edited: Sep 22, 2007
11. Sep 22, 2007

### Cyrus

What if this airplane were on a conveyor belt on takeoff?

12. Sep 22, 2007

### neutrino

:rofl: It wouldn't take off! :tongue:

13. Sep 22, 2007

### Cyrus

Noooooooooooooooooooooooooooooooooooooooooo.

14. Sep 22, 2007

### out of whack

Edited: I forgot about the invisible color thingie...

I would try to estimate it based on the tire pressure and the contact area of all tires...

Last edited: Sep 22, 2007
15. Sep 22, 2007

### genneth

How long should I wait before writing down the "correct" answer?

16. Sep 22, 2007

### Jimmy Snyder

I'm afraid it's already too late. I posted it myself. If you have an incorrect answer you would like to post, do so at your convenience.

17. Sep 22, 2007

### Rogerio

I think the first step would be measuring the pressure of the tires...

18. Sep 22, 2007

### treborly45

measure the wingspan, find out how much the wings can lift at different speeds. Jump in the plane and start going down the runway until it takes off. Take into account wind speed.

19. Sep 22, 2007

### dontdisturbmycircles

First off you will need to search the airport and check if they have a scale. If not you will have to build a scale, it should not be too hard as there are many useful items in the plane such as springs which could be used to construct a way of measuring mass. You will also need to find something of known mass.

I don't know about you guys but I ussually carry dynamite in my toolbox, but there is probably something at the airport which you could use as to construct explosive(fertilizer and jet fuel?) with enough time to do so.

Place the plane in the hangar, hopefully the hangar is has pretty strong walls. Now just plant enough explosive in the plane to fragment it into small pieces. Does not have to do a perfect job, some cutting can be done. Collect the ash and put it into garbage bags and measure the mass of each garbage bag. Then use a tool to cut the rest of the plane into smaller pieces if necessary and again gather the pieces into garbage bags and measure their mass. Add up the masses to get a fairly good approximation of the mass of the plane.

No one said you couldn't recruit a 100 man team to help.

(Yes I admit that my solution is not very plausible.) ;)

Last edited: Sep 22, 2007
20. Sep 23, 2007