# Simple Harmonic Motion - Two springs attached

Yeah I got this question and I'm just wondering if I'm doing it right.

## Homework Statement

A spring normally 10cm long and whose force constant is 150 n/m is connected to another spring normally 20cm long and whose force constant is 100 n/m. The combination is then pulled out so that its ends are 50cm apart.

a) find the amount each spring is stretched.

b) a 400g block on a frictionless surface is attached between the springs. find its period of oscillation.

## Homework Equations

T = 2pi sqroot(m/k)
F = kx

## The Attempt at a Solution

Well I tried something no idea if it is correct..

a) Made Xtotal = 0.2 because I subtracted the spring lengths
X1 = F/150
X2 = F/100
(F/150)+(F/100) = 0.2
F = 12
Then I subbed F values back into the original 2 equations to get X values.

b) For this question I assumed the combined force constant for the springs would be additive so
k = 250 n/m
m = 0.4 kg

T = 2pi sqroot (m/k)
= 2pi sqroot (0.4/250)
= 0.25s (approx)

Need to know if I'm doing this right or horribly wrong..

Cheers

ehild
Homework Helper
It is OK.

ehild

Does that means i've done it right??

ehild
Homework Helper
Does that means i've done it right??

YES!!!! ehild