Thermal expansion on a spring?

[rsyodoom2005]

1. A brass spring has an unstrained length of .18m and a spring constant of 1.3 E4 N/m. THe temperature increases from 21 cel to 135 cel. what is the magnitude of the compressional force that must be applied to the heated spring to bring it back to its original lenght!?



2. Linear expansion; Change of lenght= constant *lenght * change of temp
F= K Change of lenght




the thing i am concern is with Linear expansion formula can i use this fromula for the spring?! I figure out my change of length first my multyplying my coeficcient of brass
(9*10^-6)* .18m * 135-21 to get a result of 3.89*10^-4

Then i clicked it on to the spring constan formula using F= 1.3*10^4 * the distance of 3.89*10^-4 to myforce of 5.07N... is this a right approach?

 

[azatkgz]

Must be correct.I don't think that this question needs more complicated solution.

 

[ogb p]

Yes, your approach is correct. The formula for linear expansion can be used for a spring, as the spring will experience a change in length due to the change in temperature. Your calculation of the change in length is correct and using the spring constant formula to calculate the force needed to bring the spring back to its original length is also correct. The compressional force needed would be 5.07N.