# Homework Help: Spring constant/kinetic energy

1. Jul 17, 2009

### kavipach

1. The problem statement, all variables and given/known data

If you stand on a bathroom scale, the spring inside the scale compresses 0.55mm, and it tells you your weight is 760 N.
Now if you jump on the scale from a height of 1.3m, what does the scale read at its peak?

2. Relevant equations
F=kx
K.E=1/2mv^2

3. The attempt at a solution
I tried alot of things but i cant get the answer

2. Jul 17, 2009

### wavingerwin

Try more...

Well one more equation you need to know

Elastic potential energy = Eep = 0.5 kx2

I'm sure you know how to get the spring constant, k
And then find the total energy of the system E = mgh

then substitute the E value you got to the equation
Eep = 0.5 kx2 to find x

(at the "peak", all of the kinetic energy + gravitational potential energy is converted to elastic potential energy)

then since you know the x (compression) at the peak value
substitute to F = kx to get the F value for the scale value it reads

That's what i would do.
I can very well be wrong

3. Jul 17, 2009

### songoku

4. Jul 18, 2009

### JazzFusion

Very well explained, V_B!

5. Jul 18, 2009

Thx LOL ^^