Elastic Potential Energy

In summary, the conversation discusses the best graph to illustrate potential energy vs. time for a system involving a box on a spring. The answer is A and the question is raised as to why elastic potential energy cannot be negative. The response explains that energy is never negative and the equation for elastic potential energy, ½kx2, does not result in a negative value when x is negative.
  • #1
Joseph Phan
10
0
Screen%20Shot%202017-06-18%20at%205.57.22%20PM_zpsud1w1rvc.png


Screen%20Shot%202017-06-18%20at%205.57.12%20PM_zpskyksz9kc.png


Screen%20Shot%202017-06-18%20at%205.57.12%20PM_zpskyksz9kc.png

Homework Statement


Which of the following Graphs BEST illustrates the potential energy vs. time for the system in Figure 1, where t=0 is defined as the time at which the incident box 1st contacts the box on the spring?

My question is why can't the Elastic PE be negative?
The answer is A

Homework Equations


Using Conservation of Energy
1/2mv2 = 1/2kx2

The Attempt at a Solution


I Choose C because I knew that at the start, all the energy would be kinetic energy, thus the potential energy must be 0. In addition, I also knew that the graph of a spring must be a sin or cos graph. Once the spring was compressed to the right, it would be positive. However, once the spring travels to the left wouldn't the PE be negative, since the displacement would be negative once it passed the equilibrium point in the spring?

Thanks.
 
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  • #2
Joseph Phan said:
why can't the Elastic PE be negative?
Because energy is never negative, unless you are expressing relative energy levels.
Joseph Phan said:
since the displacement would be negative once it passed the equilibrium point in the spring?
The elastic PE is ½kx2. If x is negative, does that make that expression negative?
 

1. What is elastic potential energy?

Elastic potential energy is a type of potential energy that is stored in an object when it is stretched or compressed due to a force acting on it.

2. How is elastic potential energy different from other types of potential energy?

Elastic potential energy is different from other types of potential energy, such as gravitational potential energy or chemical potential energy, because it is related to the deformation of an object rather than its position or chemical composition.

3. What factors affect the amount of elastic potential energy in an object?

The amount of elastic potential energy in an object is affected by the amount of deformation (stretching or compression) of the object and the stiffness of the material it is made of.

4. How is elastic potential energy calculated?

The formula for calculating elastic potential energy is PE = 1/2 * k * x^2, where PE is the elastic potential energy, k is the spring constant of the material, and x is the amount of deformation.

5. What are some real-life examples of elastic potential energy?

Some real-life examples of objects that store elastic potential energy include a stretched rubber band, a compressed spring, and a bent bow and arrow.

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