Spring Problem and average force

In summary: So using the formula E_p = F_{avg} x, we get E_p = 5.7N(1.3cm) = 7.41 mJ, which is approximately 1/2 the value you got. Therefore, the value of 3.1 m/s is correct and you did not go wrong.
  • #1
temaire
279
0

Homework Statement


http://img88.imageshack.us/img88/9351/springny2.jpg​
[/URL]


Homework Equations


[tex]E_p = \frac{Fx}{2}[/tex]
[tex]E_k = \frac{mv^2}{2}[/tex]

The Attempt at a Solution


http://img231.imageshack.us/img231/4773/worknd6.jpg​
[/URL]

I get 2.22 m/s, but the answer key says 3.1 m/s. Where did I go wrong?
 
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  • #2
The average force is already given as 5.7N. You mistakenly divided it again by 2. E_p = F_avg(x)
 
  • #3
Check your value for Force. The problem gives average force...this is not equal to the actual force when the spring is compressed 1.3 cm.
 
  • #4
So Phanthom, you're saying that [tex]E_p = F_{ave}x[/tex] is an actual formula?
 
  • #5
temaire said:
So Phanthom, you're saying that [tex]E_p = F_{ave}x[/tex] is an actual formula?
The elastic potential energy stored in a spring is equal in magnitude to the work done by it when moving from its compressed distance, x, to its original uncompresed length, that is, [tex]E_p = \int Fdx[/tex], from the definition of work, where F, from Hookes Law, is [tex] F =kx [/tex]. Performing the calculus, you get the well known equation for the elastic potential energy of the spring, [tex]E_p =1/2kx^2[/tex]. Noting that [tex]F=kx[/tex] at its max compressed point, this is identically equivalent to [tex]E_p = F/2 (x) [/tex], or [tex]E_p = F_{avg} x[/tex].
In your problem, the average force is given as 5.7N. This means the force in the spring is 0 in its uncompressed length, and 11.4N when it is compressed 1.3cm.
 

1. What is the Spring Problem?

The Spring Problem is a physics concept that involves calculating the displacement, velocity, and acceleration of an object attached to a spring and released from a certain height.

2. How do you solve the Spring Problem?

To solve the Spring Problem, you will need to use the formula F = -kx, where F represents the force exerted by the spring, k is the spring constant, and x is the displacement of the object from its equilibrium position.

3. What is average force in relation to the Spring Problem?

The average force in the Spring Problem refers to the average amount of force exerted by the spring on the object as it moves from its initial position to its final position.

4. Can you explain the relationship between spring constant and average force?

The spring constant and average force have a direct relationship. This means that as the spring constant increases, the average force exerted by the spring also increases, and vice versa.

5. How does the mass of the object affect the Spring Problem and average force?

The mass of the object attached to the spring does not affect the spring constant or average force. However, it does affect the displacement, velocity, and acceleration of the object as it moves due to the force exerted by the spring.

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