# Simple harmonic motion/static equilibrium -spring problem, mass given

1. Apr 23, 2013

### mariegrdnr

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

A 0.500 kg mass is suspended from a spring and set into
oscillatory motion. A motion detector is used to record the motion, and it is found that its velocity function is given by Vx(t) What are:
a. the period of the motion;
b. the amplitude;
c. the maximum acceleration of the mass; and
d. the force constant of the spring?

2. Relevant equations
given
Vx(t)=-ωAsin(ωt+$\phi$)
not given but seems like the way I need to head
Fspring=-k$\Delta$y
T=2pi$\sqrt{m/k}$
3. The attempt at a solution
Did FBD where Fspring=-k$\Delta$y is straight up and weight=4.9N goes straight down. Giving Fnety=
K$\Delta$L-mg=0
K$\Delta$L=mg? can I make this assumption or am I missing something?
Also I have three unknowns k,$\Delta$L, T and cant find another equation to substitute into for third variable. I just need to know if I am heading in the right direction for this problem.
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Apr 23, 2013

### rl.bhat

To solve the problem, one more data is essential.

3. Apr 23, 2013

### mariegrdnr

Yes I agree, but none was given, so I was hoping that someone might see something:-(
Thank you for taking a look!

4. Apr 24, 2013

### rude man

No, I believe it can be solved with the given info, provided that the mass was set in motion in the usual way by imparting an initial displacement to the system at rest.

Hint: determine x(t) and dx/dt as functions of time. Determine maximum dx/dt. Then determine time t1 at which dx/dt is half of max. This I believe allows solving for every parameter.