Need help finding spring constant

[Mustrdhead]

Homework Statement

A 147g ball is dropped from a height of 56.5cm above a spring of neglibible mass. The ball compresses the spring to a maximum displacement of 4.45393cm. The acceleration is 9.8m/s^2. calculate the spring force constant k. Answer in units of N/m.

Homework Equations

Not sure

The Attempt at a Solution

I converted the mass from 147g to .147kg the height from 56.5cm to .565m and the displacement from 4.45393cm to .0445393m.

Now I am stuck and don't know what to do

I tried mgh=.5kx^2 but didnt work

 

[Doc Al]

I tried mgh=.5kx^2 but didnt work

What did you use for h? (You need the change in height, from initial position to final position.)

 

[Mustrdhead]

what do you mean? i used the given height of .565m

 

[Doc Al]

Hint: What's the change in gravitational PE? Hint 2: Measure gravitational PE from the lowest point.

 

[Mustrdhead]

so use a zero height? or use .565+.0445393?

 

[Doc Al]

or use .565+.0445393?

That's the height you need to use in that formula. This is just a consequence of conservation of energy.

 

[Mustrdhead]

Thanks you are a genius

 

[Doc Al]

Thanks you are a genius

You are very perceptive. :rofl: