1. Oct 13, 2008

### mathgirl2007

A 20-kg mass was initially at rest, attached to the end of a vertically hanging spring. When given an initial downward velocity of 2 m/s from its equilibrium rest position, the mass was observed to attain a maximum displacement of 0.2m from its equilibrium position. What is the value of the spring constant k?

Please help me. I cannot figure this one out. I think the equation is just mg-kdeltay=0 but I cant figure it out. I know 20 kg is the mass. w=mg=20(9.8)=196.

2. Oct 13, 2008

### LowlyPion

If it has velocity, it has kinetic energy. The kinetic energy will get absorbed by the retarding force of the spring as the velocity slows. When the velocity goes to 0, the spring should be at maximum displacement.

3. Oct 13, 2008

### mathgirl2007

i really dont understand this one.
can someone please just explain how to find k for me

4. Oct 13, 2008

### LowlyPion

What is the kinetic energy of the mass when it is moving at 2 m/s?

When that kinetic energy is reduced to 0 by the spring, how much potential energy is then stored in the spring. (Hint: Conservation of Energy)

What is the formula for potential energy stored in a spring? (Hint: It involves the spring constant k.)