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Find maximum speed of mass on spring

  • #1
197
3

Homework Statement



Find the maximum speed of the mass on a spring.

The spring and mass are lying on a horizontal surface, with the spring being attached to both the wall and mass. The mass is 8kg and the spring constant is 784 N/m. The spring, at resting state, is 20cm (0.2m), but the spring is currently stretched to 25cm (.25m).

f (frequency) is 1.576 Hz (this I calculated, it was not given so it could be wrong.).


Homework Equations



I found this EQ online for Vmax: fA = 2pi

f = frequency
A = amplitude

The Attempt at a Solution



I was think of using the above formula, but I don't know how to find the Amplitude.

I have taken AP Calculus AB, but the Physics course I am taking is non- calculus based, so please try not to explain in calculus terms.

I do know that the mass has the maximum velocity right when it passes the equilibrium point.

Thanks!

*wait, i just saw you can solve for A from the fA=2pi. But how does this formula work for a spring if I have all the variables for the formula?
 

Answers and Replies

  • #2
Delphi51
Homework Helper
3,407
10
Do you have formulas for the motion of the mass like this:
http://hyperphysics.phy-astr.gsu.edu/hbase/shm.html#c1
There is a similar one for the velocity, which you could obtain by differentiating that one.

Or you could take an energy approach. The mass initially has spring energy. That is entirely converted into kinetic energy at the point where the speed is greatest. If you have formulas for spring and kinetic energy, that's probably the easiest approach.
 
  • #3
197
3
to use the kinetic and spring energy approach, how would I do that?

I know that kinetic energy (Fk) is .5m(v^2).

Is Spring energy .5k(x^2)?
 
  • #4
Delphi51
Homework Helper
3,407
10
Initial spring energy = maximum kinetic energy
 

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