• Support PF! Buy your school textbooks, materials and every day products Here!

Potential Energy and Spring

  • Thread starter soul5
  • Start date
  • #1
64
0

Homework Statement



A block of mass m = 3.4 kg is dropped from height h = 44 cm onto a spring of spring constant k = 1920 N/m (Fig. 8-38). Find the maximum distance the spring is compressed.

[PLAIN]http://edugen.wiley.com/edugen/courses/crs1650/art/qb/qu/c08/fig08_36.gif [Broken]



Homework Equations



Ep=mgh

Ep=1/2kx^2



The Attempt at a Solution





Ok so I found the Potential Energy Ep=mgh. That energy should equal to 1/2kx^2.

So I set mgh = 1/2kx^2 to solve for x but my answer was wrong?

Homework Statement





Homework Equations





The Attempt at a Solution

 
Last edited by a moderator:

Answers and Replies

  • #2
167
0
Your choice to use kinetic and potential energy is correct, but you are missing one small thing.

The distance the block moves down along the spring (that is, the distance the spring is displaced x) still counts as gravitational potential energy for the block. So modifying the equation you have to take this into account will yield:

mg(h+x) = .5kx^2

From here you can solve for x, the displacement of the spring. Since it is a quadratic, you will get 2 different answers, but it should be clear which one is the correct answer.
 
  • #3
29
0
What was your answer for x, I got 0.1236m.
 
  • #4
64
0
What was your answer for x, I got 0.1236m.


that's what I got to the first time, but it was wrong......
 
  • #5
167
0
if you try what I mentioned you will get x=.142m which I believe is the correct answer.
 

Related Threads for: Potential Energy and Spring

  • Last Post
Replies
1
Views
877
  • Last Post
Replies
5
Views
2K
  • Last Post
Replies
3
Views
621
  • Last Post
Replies
2
Views
89
  • Last Post
Replies
3
Views
1K
Replies
1
Views
2K
  • Last Post
Replies
8
Views
2K
  • Last Post
Replies
10
Views
6K
Top