Find the maximum elastic potential energy of the spring

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Homework Help Overview

The problem involves a 2.0 kg mass compressed against a spring with a spring constant of 800 N/m, which is released to move along a frictionless surface and up a slope. The original poster seeks to calculate the maximum elastic potential energy of the spring, the maximum velocity of the mass, and the maximum height the mass will reach on the slope.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • The original poster calculates the maximum elastic potential energy using the formula E_p = (1/2)kx^2 and expresses uncertainty about their results. They also raise questions about notation for potential energy and the use of the multiplication sign. Other participants confirm the calculations and discuss the meaning of "maximum" in the context of the quantities being calculated.

Discussion Status

The discussion includes confirmations of the original poster's calculations and clarifications regarding the concept of maximum values in relation to the spring potential energy, mass speed, and height. Participants are exploring the implications of the term "maximum" and how it relates to the varying nature of the quantities involved.

Contextual Notes

There is a focus on notation and the definitions of terms used in the calculations. The original poster has not completed all parts of the problem and is seeking further clarification on the concepts involved.

TheShapeOfTime
A 2.0 kg mass is pressed against a spring (k = 800N/m) such that the spring has been compressed 0.22 m. The spring is released and the mass moves along a horizontal frictionless surface and up a frictionless slope. Calculate:
a) the maximum elastic potential energy of the spring
b) the maximum velocity of the mass
c) the maximum vertical height the mass will travel up the slope

This is what I've done so far (I'm not sure if it's correct):
[tex]E_p spring = \frac{1}{2}kx^2[/tex]
[tex]= \frac{1}{2} \cdot 800 \cdot 0.22^2[/tex]
[tex]= 19.36J[/tex]

[tex]E_p spring = E_k mass[/tex]
[tex]\frac{1}{2}kx^2 = \frac{1}{2}mv^2[/tex]
[tex]v = 4.4m/s^2[/tex]

Few notation questions:

What is the appropriate notation for [itex]E_p spring[/itex]?
Is it ok to use "[itex]\cdot[/itex]" in place of the regular multiplication sign whereever?
 
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What you've done so far looks correct to me as well, as long as you understand why they're using the adjective "maximum" to describe the quantities you're calculating. :)
The [tex]\cdot[/tex] is fine to use between numbers in R, as the multiplication operator satisfies the definition of the dot product on R. You can use Us to represent potential energy of the spring if you want to use a common potential energy symbol, but as long as you define your notation and its not unnecessarily convoluted, it's fine to use. :)
 
Thanks for checking over my work! I hadn't completed (c) because I wasn't sure how to do it, but I found out today it was just me forgetting about one formula I had:

[tex]E_p = mgh[/tex]
[tex]h = \frac{E_p}{mg}[/tex]
[tex]= \frac{19}{2.0 \cdot 9.80}[/tex]
[tex]= 0.97m[/tex]

Could you elaborate a bit on the adjective "maximum" and why it's used? Why might there be lesser values than the ones I calculated with these formula's?
 
TheShapeOfTime said:
Could you elaborate a bit on the adjective "maximum" and why it's used? Why might there be lesser values than the ones I calculated with these formula's?
The quantities in question (spring PE, speed of mass, height up the slope) are not constants. For example, since spring PE is [itex]1/2k x^2[/itex], it varies from zero to some maximum value (at [itex]x = x_{max}[/itex]).
 
Oh, so they were asking for the maximum EP, etc. with the values they provided?
 

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