# Homework Help: Physics 20-1: Energy

1. Jan 8, 2009

### physicznoob

1. The problem statement, all variables and given/known data
This is a question from a test i had today..i wanna know if I did it right or not.

A mass on a spring with spring constant 700 N/m is compressed 16 cm. If the maximum value of the speed is 12 m/s, what is the mass of the mass in kg?

2. Relevant equations

Ep = 1/2kx^2, Ek = 1/2mv^2

3. The attempt at a solution

so conservation of energy plays a role in this...

Vmax = 12 m/s
k = 700 N/m
x = 0.16 m
m = ?

Ep = Ek
1/2kx^2 = 1/2mv^2
m = (1/2kx^2) / (1/2v^2)
m = 0.12 kg.

im really doubting myself right now.

2. Jan 9, 2009

### NBAJam100

Looks ok to me, but then again it is 1:30 A.M and im borderline asleep...

3. Jan 9, 2009

### physicznoob

lol. well thanks i guess. but a whole bunch of other people in my class got something else. it's wierd.

4. Jan 9, 2009

### scienture

Did the problem statement tell that whether the spring was vertical or horizonal?
if it's vertical ,the answer will be different.