# Damped Harmonic Motion - Oscillating Spring

1. Apr 8, 2013

### elemis

1. The problem statement, all variables and given/known data

http://www.mediafire.com/view/?7045cz9au1ci7cd

A mountain bike has bad shock absorbers (w0/γ = 10) that oscillate with a period of 0.5 seconds after hitting a bump. If the mass of the bike and rider is 80kg, determine the value
of the spring constant k (remembering that there are two springs that share the mass equally).

3. The attempt at a solution

2pi/0.5 = w = 4pi But w = √(k/m)

16pi2 * 80 = k = 12633.

Since the two springs are in parallel we have the spring constant for an individual spring = 6317 N/m

Last edited: Apr 9, 2013
2. Apr 8, 2013

### rude man

Might be OK but I can't read what it said in parentheses after " ...bad shock absorbers ...".

3. Apr 8, 2013

### elemis

Its basically saying that the quality factor = 10

Could I have another opinion, please ?

Here's the entire question if you need it :

http://www.mediafire.com/view/?7045cz9au1ci7cd

Last edited: Apr 9, 2013
4. Apr 9, 2013

### rude man

Couldn't open the link. But, no matter, you said Q = 10.

Which is a pretty high Q but still the fact that it's not infinite means your computation of k is off by a bit.

You first need to compute your natural frequency which = sqrt(k/m). Hint: it's not 2pi/0.5 rad/s. Close, but not equal to.

Use your knowledge of Q to get the natural frequency & then you're home free.

5. Apr 9, 2013