# Simple Harmonic Motion - Two springs attached

Koey
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

## Answers and Replies

Homework Helper
It is OK.

ehild

Koey
Does that means i've done it right??

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

YES!!!! ehild