4 ms·

but what you're saying is that the spring can't distinguish between the setup on the right and the setup on the left. that doesn't seem right. if you detach on

by exit 16y ago

but what you're saying is that the spring can't distinguish between the setup on the right and the setup on the left. that doesn't seem right. if you detach one of the weights and anchor it on the other weight, the balance should read 2kg. and if you anchor weight A on the string of weight B, it would also read 2kg. as you move weight A's anchor point closer and closer to the balance, the reading remains 2kg. what happens when the anchoring point reaches the balance?

jazzychad 16y ago
> you're saying is that the spring can't distinguish between the setup on the right and the setup on the left. Correct, because according to the balance, both setups are indistinguishable. The dark secret of spring balances is that they measure (and display) force in only one direction. In stasis, the net forces on the balance are exactly zero N since there are equal and opposite forces acting upon the balance (true in each setup), yet the needle moves because it is measuring the movement (stretching) of the spring inside the balance (which at one end is anchored internally to the balance casing, and the other end is anchored to the string/mass). So, as for the setup on the right, the left-hand weight is pulling on the balance with weight 1kg (9.8N), and the right-hand weight is pulling on the balance with weight 1kg (9.8N), but since the balance only displays forces in one direction, it will display 1kg (in this case it doesn't matter which direction it is measuring because the forces are 180 degrees from each other).
- dedward 16y ago
  I think that's reading a bit too much one-directionality into it. While true, it's the amount of force that's at issue here - not the direction. If a second 2kg weight were added to the "anchor" end of the spring balance - it would either register -1kg (if it's built to do that) or break or lock up givinging invalid or useless readings. Of course - assuming the balance isn't anchored anywhere else, this would set the whole system in motion, and it would all fall apart ratherquickly.

by exit 16y ago

jazzychad 16y ago

> you're saying is that the spring can't distinguish between the setup on the right and the setup on the left. Correct, because according to the balance, both setups are indistinguishable. The dark secret of spring balances is that they measure (and display) force in only one direction. In stasis, the net forces on the balance are exactly zero N since there are equal and opposite forces acting upon the balance (true in each setup), yet the needle moves because it is measuring the movement (stretching) of the spring inside the balance (which at one end is anchored internally to the balance casing, and the other end is anchored to the string/mass). So, as for the setup on the right, the left-hand weight is pulling on the balance with weight 1kg (9.8N), and the right-hand weight is pulling on the balance with weight 1kg (9.8N), but since the balance only displays forces in one direction, it will display 1kg (in this case it doesn't matter which direction it is measuring because the forces are 180 degrees from each other).

dedward 16y ago
I think that's reading a bit too much one-directionality into it. While true, it's the amount of force that's at issue here - not the direction. If a second 2kg weight were added to the "anchor" end of the spring balance - it would either register -1kg (if it's built to do that) or break or lock up givinging invalid or useless readings. Of course - assuming the balance isn't anchored anywhere else, this would set the whole system in motion, and it would all fall apart ratherquickly.