Hanging Mass on Spring

  • Thread starter moonbase
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  • #1
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Homework Statement


A spring with spring constant k = 50 N/m and unstretched length of L is attached to the ceiling. A block of mass m = 1.5 kg is hung gently on the end of the spring. How far does the spring stretch?

Homework Equations


PEspring=0.5kx2
Fspring=-kx

The Attempt at a Solution


When the mass hangs at rest at its lowest point where the spring is stretched the furthest, its weight is exerting a force of 14.7 N on the spring. Likewise, the spring should be exerting that same force on the mass, but plugging that into the force equation by dividing 14.7 by 50 gives an x value of 0.29 m, but this is incorrect. I must be overlooking something since I know I probably have to use the potential energy equation too. Any know what I'm doing wrong?
 

Answers and Replies

  • #2
gneill
Mentor
20,925
2,867
Are there any particular units that they want the result expressed in? The force balance approach should be correct.
 
  • #3
21
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Oh, apparently I was right, it was the significant figures that were saying it was wrong. Thanks anyway!
 

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