I was hoping someone could shed some light on this argument:
“If a person were to place each of their feet on two separate scales, the sum of the readings would be equal to the weight of that person.”
Personally, I think that it is true, but others here at the office disagree.
Any ideas?
I have an idea.
Try it.
Yeah, I’d like to, but the problem is I don’t have 2 truly calibrated scales (let alone 2 scales…).
BRJ
It’s true as the scales measure the pressure exerted by the fatty (which is dircetly prop. to his weight ), as all that pressure is placed on one scale or the other the sum total whether his huge bulk was equally distributed onto both scales or not would be the same.
Assuming that the feet are placed in the center of a flat plate which is supported by the weighing mechanism (none of that modern cheapness with the dip of the frame = weight! No step in a different place, lean a little bit and IT"S DIFFEENT WEEIGHT! No NO NO ! Only way to go is with the spring scale.
The sum of 2 properly calibrated scales will add up to fattie’s (or anyone for that matter) total weight.
However, depending on how thier person stands, the 2 scales might not be equal to each other. If he leans left, the left scale will register more weight weight while the right scale will reigister less. but the total of the 2 scale will always add up to the same total.
Suppose you are standing on a platform. Your body exerts some force on the platform related to your weight. The platform, in turn, exerts an equal and opposite force on your body to prevent you from moving either up or down. (More accurately, to prevent you from accelerating up or down.)
Now split the platform. Your body still exerts the same force downwards. The two platforms still have to exert the same total force upwards. That means that the two platforms have to add up to the same force, regardless of the distribution of weight, and the two scales will measure the same total weight as a single scale. You could step (slowly, smoothly – no bouncing!) from one scale to another and, at any instantaneous time, the two scales would add up to the same value.
And you thought you’d never need Newton’s Laws.
Incidentally, this is one way to weigh something that’s heavier than the maximum measurement of the scale you have. Put the item on two (or more) blocks – split the platform on which it’s resting. One at a time, replace each block with the scale and record the weight. As long as the scale exactly replaces each block, the sum of all the measurements is the weight of the object.
In this way you could measure the weight of a car by putting the scale under each wheel in turn.
Wouldn’t that be like stepping on a scale with your foot partially on the floor and partially on the scale? You would have no way of knowing how much of the weight is on the floor.
I see what your saying about something on blocks with a scale that exactly replaces the blocks. But on a car, with one scale under each wheel in turn and adding the total, I seriously doubt you could get an accurate reading. With suspension, and even without, how could that work?
And you’d have to make sure that the weight is exactly in the same place after you move the blocks–I’m assuming that you’d have to move the weight to move the blocks.
voltaire, if the weight distribution is unchanged, the four wheels can be weight independently and the total will be accurate. So my description of weighing a car is not entirely accurate: you would have to raise the entire car on blocks the thickness of the scale. In other words, you have to ensure the car is at the same attitude for all four weighings. If the car is tilted to one side for one wheel and so on, as would be the case if you simply squeezed the scale in between the wheel and the ground each time, the measurement would certainly be inaccurate. I doubt it would be off by much, though, given the thickness of the scale proportional to the width of the car.
As for moving the weight when you’re moving the blocks, RM Mentock, that also is true. If you don’t put the scale in exactly the same place that the block was sitting, you won’t get an accurate reading. For this reason it’s easier to weigh something that has definite points of contact, like the car with four wheels or a table with distinct legs, than it is to weigh something with a flat bottom. But, once again, if you exercise a bit of care you can still get a good measurement. If you need a lot of accuracy you need to be sure you use exactly the same points of contact for every weighing, but to figure out if your fridge is 60kg or 70kg, this method will do you fine.
Of course, if you have multiple scales and take the measurement instantaneously, as is the case in the OP, the weight will be accurate to the accuracy of the scale you use. (Okay, to be precise the error will be within the maximum cumulative error of the scales.)
lets not forget that one side of most peoples body is slightly bigger then the other.