# Springs in Series

"A spring that obeys Hooke's Law has a force constant of 160Nm^-1."
(c) "A second identical spring connected in series with the first, to create a single spring of twice the length ."
(i) "Calculate the extension of each spring, in mm, produced by a force of 4.0N."

I used 1/k total = 1/k1 +1/k2 and got k total = 80nm^-1, and then 80nm^-1/4.0N to = 20m/2 = 10m = 10,000mm, but that can't possibly be right. I'm not sure where I'm meant to go with this one. Could anyone please help? Thanks.
Original post by Spark3982
"A spring that obeys Hooke's Law has a force constant of 160Nm^-1."
(c) "A second identical spring connected in series with the first, to create a single spring of twice the length ."
(i) "Calculate the extension of each spring, in mm, produced by a force of 4.0N."

I used 1/k total = 1/k1 +1/k2 and got k total = 80nm^-1, and then 80nm^-1/4.0N to = 20m/2 = 10m = 10,000mm, but that can't possibly be right. I'm not sure where I'm meant to go with this one. Could anyone please help? Thanks.

Is that (bold) the right way round (think units)