How do you make a portable weighing scale using Hooke's Law?

Answer 1

Bekki is on the right track and eyeonthescreen is good too.

First compute k as was specified

k=F/x

k- spring constant
F = W=mg
m - known mass (in kg)
g - acceleration due to gravity (9.81m/s^2

Then you can make a scale such as per certain amount of mass it elongated a certain length

Let say you placed a 2 kg mass and the spring elongated 1 cm

k = 2 (9.81)/.01=1962 N/m (that is the scientific way)
or better yet mark .5 cm fro every kilogram.( he-he) that is the easiest way.

Sorry almost forgot; if you are looking for a portable scale you mast use a portable spring. ;-)

Answer 2

Bekki, per usual you are right on...I've no clue why anyone would give you a thumbs down.

I would add one thing, from an old angler, a fish scale (no, not the scale on the fish) for weighing caught fish is exactly what the asker is looking for. It uses Hookes Law and is already calibrated...usually in pounds for U.S. consumption.

Answer 3

If you have a spring of known k, just hang it on something and mark the equilibrium point.

Put a weight on there.

Measure the change in length from equilibrium. Call that x.

F = kx is your weight. Nifty!

Edit: If you don't know k, you'll need a known weight of some sort to calibrate your scale.