# Simple harmonic motion with an amplitude

1. Oct 13, 2009

### physics_geek

1. The problem statement, all variables and given/known data
A block of unknown mass is attached to a spring with a spring constant of 5.50 N/m and undergoes simple harmonic motion with an amplitude of 12.5 cm. When the block is halfway between its equilibrium position and the end point, its speed is measured to be 25.0 cm/s.

(a) Calculate the mass of the block.
(b) Calculate the period of the motion.
(c) Calculate the maximum acceleration of the block.

2. Relevant equations
Vmax = sqrt(k/m)A
T= 2pi/w
a_max = kA/m

3. The attempt at a solution
so i thought i would use the first formula i stated to find the mass of the block
but apparently im wrong.
can someone please help me get started.
thanks

2. Oct 13, 2009

### rock.freak667

Re: Oscillations

Well the total energy of the system is given by 1/2 kA2 and throughout the motion this is interchanged between elastic potential and kinetic energy. So halfway between the max point and equilibrium, how far does the spring stretch? Can you now apply a conservation of energy to get the mass?

3. Oct 13, 2009

### rl.bhat

Re: Oscillations

Show your calculations to see where you have made mistake.

4. Oct 13, 2009

### physics_geek

Re: Oscillations

well what i did was
vmax = sqrt(k/m)A
(v^2/A^2)m = k
so
m = kA^2/v^2 but i guess this is wrong

so do i use something like 1/2kA^2 = 1/2mv^2 ???

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