C-115 is a spring made by Century Corp. It stretches very easily under a mass and can stretch fairly far while retaining its shape.

The following is the correlation between the spring C-115 and how far it stretches given a specific weight/force applied. The distance coefficient corresponds to the mass in that given Newton's Second Law, F = ma, the spring will stretch the given distance (in centimeters) when experiencing an acceleration of one m/s^2 (approximately 1/10 of a g). Looking at the chart then, this means that a mass of 209 grams will stretch the spring approximately one centimeter under an acceleration of 1 m/s^2. With respects to gravity, the spring will stretch 9.81 cm under a mass of 209 grams.

This chart can be used in the calibration of an accelerometer as described on How to Build an Accelerometer.

Slope: (m) -0.96830037
Intercept: (b) 5.173931181
distco = e^(m * ln(Mass) + b)
r^2: 0.999936756
r: -0.99996838

Mass (g)Dist Coeff	Mass (g)Dist Coeff	Mass (g)Dist Coeff	
0	0	        100	2.043664887	200	1.044533416	
0.5	345.538966	100.5	2.033818932	200.5	1.042011068	
1	176.6077202	101	2.024068923	201	1.03950107	
1.5	119.2615689	101.5	2.014413459	201.5	1.037003332	
2	90.26561373	102	2.004851163	202	1.034517763		
2.5	72.72510781	102.5	1.995380687	202.5	1.032044275		
3	60.95553861	103	1.986000706	203	1.029582778		
3.5	52.50354126	103.5	1.976709923	203.5	1.027133186		
4	46.13547479	104	1.967507066	204	1.024695413		
4.5	41.1627145	104.5	1.958390885	204.5	1.022269371		
5	37.17038237	105	1.949360155	205	1.019854976		
5.5	33.89350572	105.5	1.940413675	205.5	1.017452145		
6	31.15486173	106	1.931550263	206	1.015060793		
6.5	28.83139663	106.5	1.922768763	206.5	1.012680839		
7	26.8349785	107	1.914068038	207	1.0103122		
7.5	25.10081729	107.5	1.905446973	207.5	1.007954796		
8	23.58020896	108	1.896904474	208	1.005608547		
8.5	22.23582964	108.5	1.888439465	208.5	1.003273372		
9	21.03859154	109	1.880050891	209	1.000949194		
9.5	19.9654874	109.5	1.871737716	209.5	0.998635934		
10	18.99807876	110	1.863498923	210	0.996333516		
10.5	18.12141413	110.5	1.855333513	210.5	0.994041863		
11	17.32324098	111	1.847240505	211	0.991760898		
11.5	16.59342226	111.5	1.839218934	211.5	0.989490548		
12	15.9234982	112	1.831267854	212	0.987230738		
12.5	15.30635276	112.5	1.823386335	212.5	0.984981394		
13	14.73595666	113	1.815573463	213	0.982742443		
13.5	14.20716733	113.5	1.807828341	213.5	0.980513814		
14	13.71557145	114	1.800150086	214	0.978295433		
14.5	13.25735992	114.5	1.792537832	214.5	0.976087232		
15	12.82922783	115	1.784990727	215	0.973889139		
15.5	12.42829349	115.5	1.777507934	215.5	0.971701084		
16	12.05203279	116	1.770088629	216	0.969522999		
16.5	11.69822528	116.5	1.762732004	216.5	0.967354815		
17	11.3649098	117	1.755437264	217	0.965196465		
17.5	11.05034764	117.5	1.748203627	217.5	0.963047882		
18	10.75299186	118	1.741030324	218	0.960908998		
18.5	10.47146147	118.5	1.7339166	218.5	0.958779749		
19	10.20451978	119	1.726861712	219	0.956660068		
19.5	9.951055981	119.5	1.719864929	219.5	0.954549892		
20	9.710069509	120	1.712925531	220	0.952449156		
20.5	9.480656681	120.5	1.706042813	220.5	0.950357796		
21	9.261999229	121	1.699216079	221	0.94827575		
21.5	9.053354429	121.5	1.692444646	221.5	0.946202954		
22	8.854046566	122	1.685727839	222	0.944139348		
22.5	8.663459536	122.5	1.679064998	222.5	0.94208487		
23	8.481030401	123	1.672455472	223	0.94003946		
23.5	8.30624377	123.5	1.665898619	223.5	0.938003056		
24	8.138626875	124	1.659393809	224	0.935975599		
24.5	7.97774525	124.5	1.652940422	224.5	0.933957031		
25	7.82319892	125	1.646537846	225	0.931947292		
25.5	7.674619041	125.5	1.640185482	225.5	0.929946325		
26	7.531664928	126	1.633882737	226	0.927954071		
26.5	7.394021411	126.5	1.62762903	226.5	0.925970474		
27	7.261396486	127	1.621423788	227	0.923995477		
27.5	7.133519226	127.5	1.615266445	227.5	0.922029025		
28	7.010137908	128	1.609156447	228	0.92007106		
28.5	6.891018337	128.5	1.603093247	228.5	0.918121529		
29	6.775942347	129	1.597076306	229	0.916180377		
29.5	6.66470645	129.5	1.591105095	229.5	0.914247548		
30	6.557120618	130	1.585179091	230	0.912322991		
30.5	6.453007191	130.5	1.579297779	230.5	0.910406651		
31	6.352199882	131	1.573460655	231	0.908498476		
31.5	6.254542879	131.5	1.567667218	231.5	0.906598412		
32	6.159890038	132	1.561916978	232	0.90470641		
32.5	6.068104134	132.5	1.55620945	232.5	0.902822416		
33	5.979056199	133	1.550544159	233	0.90094638		
33.5	5.892624903	133.5	1.544920634	233.5	0.899078252		
34	5.808696	134	1.539338413	234	0.89721798		
34.5	5.727161814	134.5	1.53379704	234.5	0.895365516		
35	5.647920775	135	1.528296066	235	0.893520811		
35.5	5.570876993	135.5	1.522835048	235.5	0.891683814		
36	5.495939863	136	1.517413551	236	0.889854479		
36.5	5.423023705	136.5	1.512031145	236.5	0.888032756		
37	5.352047437	137	1.506687405	237	0.886218598		
37.5	5.282934266	137.5	1.501381916	237.5	0.884411957		
38	5.215611411	138	1.496114265	238	0.882612788		
38.5	5.150009843	138.5	1.490884047	238.5	0.880821043		
39	5.086064043	139	1.485690862	239	0.879036676		
39.5	5.023711787	139.5	1.480534316	239.5	0.877259642		
40	4.962893936	140	1.475414021	240	0.875489895		
40.5	4.90355425	140.5	1.470329593	240.5	0.87372739		
41	4.845639211	141	1.465280656	241	0.871972083		
41.5	4.789097859	141.5	1.460266837	241.5	0.870223929		
42	4.733881644	142	1.455287769	242	0.868482885		
42.5	4.679944281	142.5	1.45034309	242.5	0.866748906		
43	4.627241623	143	1.445432442	243	0.865021951		
43.5	4.575731536	143.5	1.440555475	243.5	0.863301975		
44	4.525373786	144	1.43571184	244	0.861588938		
44.5	4.476129934	144.5	1.430901196	244.5	0.859882795		
45	4.427963235	145	1.426123205	245	0.858183506		
45.5	4.380838549	145.5	1.421377534	245.5	0.85649103		
46	4.33472225	146	1.416663853	246	0.854805325		
46.5	4.289582147	146.5	1.41198184	246.5	0.85312635		
47	4.245387409	147	1.407331174	247	0.851454065		
47.5	4.202108494	147.5	1.40271154	247.5	0.84978843		
48	4.159717078	148	1.398122626	248	0.848129405		
48.5	4.118186	148.5	1.393564126	248.5	0.84647695		
49	4.077489197	149	1.389035737	249	0.844831027		
49.5	4.037601651	149.5	1.38453716	249.5	0.843191596		
50	3.998494346	150	1.380068099	250	0.84155862		
50.5	3.960159171	150.5	1.375628264	250.5	0.839932059		
51	3.922558975	151	1.371217367	251	0.838311876		
51.5	3.885677419	151.5	1.366835125	251.5	0.836698033		
52	3.849493988	152	1.362481258	252	0.835090493		
52.5	3.813988945	152.5	1.35815549	252.5	0.833489218		
53	3.779143289	153	1.353857548	253	0.831894173		
53.5	3.744938726	153.5	1.349587164	253.5	0.83030532		
54	3.711357633	154	1.345344071	254	0.828722624		
54.5	3.678383029	154.5	1.341128008	254.5	0.827146048		
55	3.645998546	155	1.336938715	255	0.825575557		
55.5	3.614188401	155.5	1.332775938	255.5	0.824011116		
56	3.582937371	156	1.328639423	256	0.822452688		
56.5	3.552230766	156.5	1.324528922	256.5	0.820900241		
57	3.522054408	157	1.320444189	257	0.819353739		
57.5	3.492394611	157.5	1.316384981	257.5	0.817813147		
58	3.463238152	158	1.312351058	258	0.816278432		
58.5	3.434572262	158.5	1.308342184	258.5	0.814749561		
59	3.406384598	159	1.304358124	259	0.813226499		
59.5	3.37866323	159.5	1.300398649	259.5	0.811709213		
60	3.351396622	160	1.296463528	260	0.810197671		
60.5	3.324573617	160.5	1.292552539	260.5	0.808691839		
61	3.29818342	161	1.288665457	261	0.807191685		
61.5	3.272215585	161.5	1.284802064	261.5	0.805697178		
62	3.24666	        162	1.280962142	262	0.804208284		
62.5	3.221506875	162.5	1.277145476	262.5	0.802724973		
63	3.196746728	163	1.273351856	263	0.801247213		
63.5	3.172370372	163.5	1.269581072	263.5	0.799774972		
64	3.148368906	164	1.265832917	264	0.798308219		
64.5	3.124733703	164.5	1.262107187	264.5	0.796846924		
65	3.101456399	165	1.258403681	265	0.795391056		
65.5	3.078528883	165.5	1.254722198	265.5	0.793940585		
66	3.055943289	166	1.251062543	266	0.792495481		
66.5	3.033691985	166.5	1.24742452	266.5	0.791055713		
67	3.011767565	167	1.243807938	267	0.789621252		
67.5	2.99016284	167.5	1.240212606	267.5	0.788192069		
68	2.968870833	168	1.236638336	268	0.786768135		
68.5	2.947884767	168.5	1.233084944	268.5	0.785349419		
69	2.927198061	169	1.229552245	269	0.783935895		
69.5	2.90680432	169.5	1.226040058	269.5	0.782527532		
70	2.886697334	170	1.222548206	270	0.781124303		
70.5	2.866871065	170.5	1.219076509	270.5	0.779726179		
71	2.847319643	171	1.215624794	271	0.778333133		
71.5	2.828037364	171.5	1.212192887	271.5	0.776945137		
72	2.809018678	172	1.208780619	272	0.775562163		
72.5	2.79025819	172.5	1.205387818	272.5	0.774184184		
73	2.771750649	173	1.20201432	273	0.772811172		
73.5	2.753490947	173.5	1.198659957	273.5	0.771443101		
74	2.735474112	174	1.195324568	274	0.770079944		
74.5	2.717695307	174.5	1.192007991	274.5	0.768721675		
75	2.70014982	175	1.188710067	275	0.767368266		
75.5	2.682833064	175.5	1.185430636	275.5	0.766019693		
76	2.665740572	176	1.182169545	276	0.764675928		
76.5	2.648867993	176.5	1.178926638	276.5	0.763336946		
77	2.632211087	177	1.175701763	277	0.762002722		
77.5	2.615765725	177.5	1.172494768	277.5	0.760673229		
78	2.599527879	178	1.169305506	278	0.759348444		
78.5	2.583493628	178.5	1.166133829	278.5	0.758028339		
79	2.567659144	179	1.16297959	279	0.756712892		
79.5	2.552020699	179.5	1.159842646	279.5	0.755402076		
80	2.536574656	180	1.156722854	280	0.754095868		
80.5	2.521317466	180.5	1.153620073	280.5	0.752794243		
81	2.506245669	181	1.150534164	281	0.751497177		
81.5	2.491355889	181.5	1.147464988	281.5	0.750204645		
82	2.476644831	182	1.144412409	282	0.748916625		
82.5	2.462109279	182.5	1.141376292	282.5	0.747633092		
83	2.447746095	183	1.138356503	283	0.746354022		
83.5	2.433552215	183.5	1.135352911	283.5	0.745079393		
84	2.419524647	184	1.132365385	284	0.74380918		
84.5	2.405660471	184.5	1.129393795	284.5	0.742543362		
85	2.391956831	185	1.126438015	285	0.741281915		
85.5	2.378410943	185.5	1.123497916	285.5	0.740024817		
86	2.365020083	186	1.120573375	286	0.738772044		
86.5	2.35178159	186.5	1.117664266	286.5	0.737523575		
87	2.338692866	187	1.114770469	287	0.736279388		
87.5	2.32575137	187.5	1.111891861	287.5	0.735039459		
88	2.312954619	188	1.109028323	288	0.733803767		
88.5	2.300300184	188.5	1.106179736	288.5	0.732572291		
89	2.287785693	189	1.103345983	289	0.731345009		
89.5	2.275408825	189.5	1.100526947	289.5	0.730121899		
90	2.26316731	190	1.097722513	290	0.728902939		
90.5	2.251058928	190.5	1.094932568	290.5	0.72768811		
91	2.239081507	191	1.092157	291	0.726477389		
91.5	2.227232924	191.5	1.089395696	291.5	0.725270756		
92	2.215511099	192	1.086648546	292	0.724068189		
92.5	2.203913999	192.5	1.083915442	292.5	0.722869669		
93	2.192439632	193	1.081196275	293	0.721675175		
93.5	2.181086052	193.5	1.078490938	293.5	0.720484686		
94	2.16985135	194	1.075799326	294	0.719298182		
94.5	2.158733659	194.5	1.073121334	294.5	0.718115644		
95	2.147731151	195	1.070456858	295	0.716937051		
95.5	2.136842036	195.5	1.067805796	295.5	0.715762383		
96	2.126064561	196	1.065168045	296	0.71459162		
96.5	2.115397008	196.5	1.062543506	296.5	0.713424744		
97	2.104837696	197	1.059932079	297	0.712261735		
97.5	2.094384976	197.5	1.057333665	297.5	0.711102573		
98	2.084037235	198	1.054748167	298	0.709947239		
98.5	2.07379289	198.5	1.052175488	298.5	0.708795714		
99	2.063650392	199	1.049615533	299	0.70764798		
99.5	2.053608221	199.5	1.047068207	299.5	0.706504017

The following shows the data used to calculate the regression line used above. Chips refer to poker chips used as incremental units during compilation.

Mass	        Grams	Kg      Dist-Coeff      J/cm    Ln(Mass)        Ln(Dist Coeff)	
00 Chips:	48.32	0.04832	4.137283226	0.19991	3.877845554	1.420039347	
05 Chips:	107.72	0.10772	1.889491733	0.20354	4.679535268	0.636307869	
10 Chips:	166.41	0.16641	1.257642275	0.20928	5.114454623	0.229238758	
15 Chips:	224.61	0.22461	0.934823153	0.20997	5.414365565	-0.06739791	
20 Chips:	284.06	0.28406	0.740954591	0.21048	5.649185483	-0.29981594	

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