Spring Problem (Hookes law)

In summary, the conversation discusses finding the spring constant and displacement of a block of mass M hanging on a vertical spring. The equations 1/2kx^2=mgx and mg=kx are used to solve for k, with the assumption that the system is stable at x. The conversation then moves on to calculating the height the block will reach when it is given velocity v from below. Finally, the conversation considers the differences in kinetic energy, gravitational potential energy, and elastic potential energy when the mass moves horizontally instead of vertically.
  • #1
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Homework Statement


A block of mass M is hung on a vertical spring.
We have to find spring constant k, x (displacement from mean position) given.

Homework Equations


1/2kx^2 = mgx
mg=kx

The Attempt at a Solution


When i conserve energy,
1/2kx^2=mgx
⇒ k= 2mg/x

But when i use mg=kx,
I get k=mg/x

But mg/x≠2mg/x,
Help please :)
 
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  • #2
You don't need to compute energy here.
Just use Hooke Law directly.

What force is M applying to the spring?
How far is this causing the spring to stretch?

The assumption here is that the system is stable at x.
 
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  • #3
.Scott said:
You don't need to compute energy here.
Just use Hooke Law directly.

What for is M applying to the spring?
How far is this causing the spring to stretch?

The assumption here is that the system is stable at x.
after that it is given some velocity v from down, i need to calculate how high will it go.
i used 1/2kx2=1/2mv2 is it correct?
 
  • #4
I love physics said:
i used 1/2kx2=1/2mv2 is it correct?
Is that based on some reasoning or just a wild guess?

If it rises above the equilibrium point by a maximum of h, what are the changes in
  1. KE
  2. GPE
  3. Elastic PE
?
 
  • #5
Consider the situation of the mass moving horizontally along a frictionless surface.
What is the difference in the two situations?
 

What is Hookes law?

Hooke's law is a scientific principle that describes the relationship between the force applied to an elastic object and the resulting deformation or change in length of that object. It states that the force applied is directly proportional to the extension or compression of the object, as long as the object's elastic limit is not exceeded.

What is the formula for Hookes law?

The formula for Hookes law is F = -kx, where F is the force applied, k is the spring constant (a measure of the stiffness of the spring), and x is the displacement or change in length of the spring.

What is the unit for the spring constant in Hookes law?

The unit for the spring constant in Hookes law is newtons per meter (N/m). This unit represents the amount of force required to stretch or compress the spring by one meter.

What is the elastic limit in Hookes law?

The elastic limit is the maximum amount of stress or force that can be applied to an object without causing permanent deformation or damage. In Hookes law, the elastic limit is the point at which the object stops obeying the principle and begins to behave in a non-linear manner.

What are some real-life examples of Hookes law?

Hookes law can be observed in many everyday objects, such as springs used in mattresses, car suspensions, and pogo sticks. It also applies to biological systems, such as the elasticity of blood vessels and tendons in the human body. Additionally, Hookes law is used in engineering and construction to determine the strength and stability of structures.

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