Plunger on compressed spring

  • Thread starter awiest82
  • Start date
  • #1
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Homework Statement



A plunger of mass m rests on a spring with constant k. The spring is pressed down a distance x and released from rest. How large does the the mass need to be in order to keep the plunger in contact with the spring?

Homework Equations



PEf+KEf=PEi

kx-mg+N=0

The Attempt at a Solution



Using the Conservation of energy equation and solving for m, I get:

kx2/(2gh+vf2) = m

I have a suspicion that I somehow have to incorporate the second equation into the answer, but am stumped as to how I proceed.
 

Answers and Replies

  • #2
Filip Larsen
Gold Member
1,360
276
Perhaps you can find a way through by analyzing the acceleration of the spring-mass and consider what limits this must be within.
 

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