# Springs, mass, speed.

1. Feb 1, 2010

### dance_sg

1. The problem statement, all variables and given/known data
a 300 g mass vibrates at the end of a horizontal spring along a frictionless surface. if the spring constant is 45N/m, and the maximum displacement of the mass is 8.0cm, what is the maximum speed of the mass?

2. Relevant equations

g=Gm/r^2

3. The attempt at a solution
do i rearrange the formula to solve for m. so it becomes m=r^2(g)/G. that only gives me the mass tho. how do i solve for the speed??

2. Feb 1, 2010

### theRIAA

I don't even know what you're doin.

Find the acceleration with F_spring=kx and F=ma.

When is the spring traveling the fastest? You should use (or combine) 3 equations to get your answer. I gave you 2.

3. Feb 1, 2010

### dance_sg

ok so,
Fspring= 45N/m(0.08m) whick is 3.6N. then arrange f=ma to solve for a, which is a=3.6N/0.3Kg, so the a is 12. then do i use the formula Vf^2=Vi^2 + 2ad. so,i would square root (2)(12)(0.08) to get 1.4 m/s as the maximum speed?

4. Feb 1, 2010

### theRIAA

if "maximum displacement" means the distance from where the spring is uncompressed, to it's maximum compression.. then yes that's right.

5. Feb 1, 2010

### dance_sg

Thank you so much :)