# Finding spring constant from a graph

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1. Jan 20, 2015

### John Sena

Assume a spring with a mass attached is oscillating.
Can i find spring constant from force/time and position/time graph using mgh=1/2kx^2?
The force in force/time graph is collected from force meter attached at the top of the spring.
The positin in position/time graph is the distance of the mass from the ground.

2. Jan 21, 2015

### Quantum Defect

If you write a function for x(t) what do you get? x(t) = x(t=0) + ... Does this expression have k anywhere? How does this relate to an important time interval?

3. Jan 21, 2015

### Staff: Mentor

Draw a free body diagram for the mass, and write a force balance for the mass. What do you get?

Chet

4. Jan 21, 2015

### ZapperZ

Staff Emeritus
There is something not quite clear here and it requires a bit more explanation.

First of all, is this something that is part of a measurement or experiment? Are you simply given a spring with a mass, and it is ALREADY oscillating? How accurate do you need this to be?

You see, if this is simply an experiment or an observation, you can easily calculate the spring constant by simply measuring the frequency of oscillation. Measure how many times the mass makes a complete oscillation in one second, and you have the frequency of oscillation. Then simply use the fact that for a SHO system,

f = (1/2pi)*(sqr(k/m)

Knowing the mass, you immediately get the value of k.

Asking if you can find the spring constant from the force-time or position-time graph is vague. Were you GIVEN these or were you asked to measure these?

Zz.