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Oscillation Problem -- Ball mass on the end of a horizontal spring

  • Thread starter osten
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  • #1
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Homework Statement


A 200 g ball attached to a spring with spring constant 2.40 N/m oscillates horizontally on a frictionless table. Its velocity is 20.0 cm/s when x=−5.00cm.
What is the amplitude of oscillation?

Homework Equations


f=√(k/m) /2π
x(t) = Acos(2πft)
v(t) = -2πfAsin(2πft)

The Attempt at a Solution


I found that t = 0.137s, and A turned out to be negative, so it was probably wrong.
 

Answers and Replies

  • #2
haruspex
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I found that t = 0.137s, and A turned out to be negative, so it was probably wrong.
You do not show your working, but there should be multiple solutions for t. Some will produce a positive A and some negative. What do you conclude from that?
 
  • #3
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Thanks! I ignored the signs and got the right answer.
 
  • #4
haruspex
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Thanks! I ignored the signs and got the right answer.
Good. Do you understand why the choice of solution for t can switch the sign?
By the way, you did not need to find t at all. You could have used sin2+cos2=1.
 

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