Weighing Ones Self

[weecalf]

Ok so you weigh your self and for sake of argument sake you are 11. 7 pounds .So as an experiment on behalf of the good people of Answerback I have weighed myself then weighed myself holding a 2 pound bag of sugar and sure enough the scales registered it although my hands were by my side and out side the width of the scales .How did that happen ?

[jim360]

1/Sqrt[5], even, or about 0.45 seconds later.

[EDDIE51]

Myth Busters have done the 'fired v dropped bullet' experiment with a real gun , and yes the 2 do hit the ground at the same time
http://scienceblogs.com/dotphysics/2009/10/09/mythbusters-bringing-on-the-physics-bullet-drop/

[weecalf]

Thanks everyone ,wouldn't it be nice if we referred to ones downwards pressure rather than weight . We could have downward pressure watchers .What is pressure gauged in ?.

[weecalf]

Jimmy stewart asked that in a film about a fly in the cockpit of the plane he was flying

[Old_Geezer]

Only if unsealed. The air pressure caused by the downswing of wings needs to escape out somehow without pressing on the truck floor.

[jim360]

Hmm... pressure and weight are two different things, sadly. Roughly speaking, pressure = weight per unit area.

It should be weight that's used on weighing scales.

[Khandro]

//yes the 2 do hit the ground at the same time//
Not really, the fired bullet hit the ground 9.2% later than the dropped bullet.
But that aside, isn't weight relative to condition? a 10 stone astronaut weighs much more than that during take-off, in space weighs nothing, and on the moon weighs only a few pounds.

[Old_Geezer]

That reminds me of a homework question from primary school along the lines of, "What weighs more, rocks or feathers ?". Something like that anyway. Multiple choice. Took quite a while to convince the teacher that the option "rocks" was not correct. That none of the options were that good, but a ton of feathers did tend to weigh more than a pound of rocks. She eventually conceded more than one option was correct, including her clearly incorrect "rocks" answer.

[Zacs-Master]

It's that thing no one can explain. Gravity.

[jim360]

Yes, although as is pointed out at numerous points in the comments this is because of effects of motion through air. Take away the air and you would have an admittedly idealised experiment, but one in which indeed the dropped bullet and the fired one would take the same amount of time to drop. Gravity doesn't act any differently on a moving object than it does on a stationary one, but if it's in motion then other forces may also be in play is all.

The other problem is of course that weight and mass get mixed up all the time. Naturally we calibrated our mass scale on earth, where mass and weight can be expressed in essentially the same units -- on the Moon a 100kg man would only "weigh" 17kg or so, while the same person on Jupiter would weight something in the region of 240kg, before he was squished into goo.

When you are accelerating your weight doesn't actually increase, ever, but over forces can act on you in the same direction to make an "effective" weight. Again, the force of Gravity isn't changing, but once in motion other forces can come into play and either act against or with gravity, or in a direction that has no effect on your weight.

[Zacs-Master]

in a direction that has no effect on your weight

What direction would that be Jim? Just curious.

[jim360]

Weight acts "down", so something at right angles to that would not have an effect on the (effective) weight of an object.

[grasscarp]

Jno, Tilly and Prudie thank you for very amusing comments

[Zacs-Master]

You mean gravity acts down? Surely weight on its own can't 'act' on anything?

[jim360]

Hmm?

Weight is just another name for the way gravity acts on a mass. Hence it's acting on any massive object, always trying to drag it to the larger object's centre of mass (also once known as the centre of gravity).

[Zacs-Master]

So you agree then? So what your saying is, something travelling at right angles is unaffected by gravity, if so it must have, according to your explanation, no weight?

[jim360]

No, that's not what I'm saying at all. I said that a force acting in a horizontal direction has no effect on your weight. That's not the same as saying that you have no weight. Or if you are travelling at a constant speed along the surface on the earth, you still have weight. Hence why it's easy to stay on the seat of a car, for example.

Weight (vertically down) is unaffected by any force acting purely horizontally, or by any horizontal motion.

[Zacs-Master]

So how come the pilot of an aircraft accelerating at right angles can feel 'g' forces?