Why is the calculated change in PE for a mass on a spring incorrect?

In summary, a spring with a length of 75cm and a mass of 0.5kg hanging from it has a spring constant of 40N/m. The extension of the spring is 0.123m and there is a change in potential energy of 0.30J, which is incorrect due to energy not being conserved.
  • #1
Emilyjoint
210
0

Homework Statement


A spring of length 75cm has a mass of 0.5kg hanging from it.
If the spring constant = 40N/m calculate:
a) the extension of the spring
b) The change in PE of the mass


Homework Equations


Part (a) is easy x = (0.5 x 9.81)/40 = 0.123m
Part (b) energy = 0.5kx^2 gives 0.30J which is WRONG !

WHY ?


The Attempt at a Solution


 
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  • #2
Hi Emilyjoint! :smile:
Emilyjoint said:
A spring of length 75cm has a mass of 0.5kg hanging from it.
If the spring constant = 40N/m calculate:

b) The change in PE of the mass

part (b) energy = 0.5kx^2 gives 0.30J which is WRONG !

that's the energy of the spring

(energy is not conserved … if you released the mass from rest, it would sail through that equilibrium position at high speed, wouldn't it? :wink:)
 

Related to Why is the calculated change in PE for a mass on a spring incorrect?

What is the definition of potential energy (PE) of weight on a spring?

The potential energy of weight on a spring is the energy that is stored in the spring when it is compressed or stretched. It is a type of elastic potential energy, which is the energy stored in an object when it is deformed.

How is the potential energy of weight on a spring calculated?

The potential energy of weight on a spring can be calculated using the equation PE = 0.5*k*x^2, where k is the spring constant and x is the displacement of the spring from its equilibrium position.

What factors affect the potential energy of weight on a spring?

The potential energy of weight on a spring is affected by the mass of the weight, the spring constant, and the displacement of the spring from its equilibrium position. The potential energy increases as any of these factors increase.

What is the relationship between potential energy of weight on a spring and the force applied?

The potential energy of weight on a spring is directly proportional to the force applied to the spring. This means that as the force increases, the potential energy also increases, and vice versa.

What are some real-life applications of the potential energy of weight on a spring?

The potential energy of weight on a spring is commonly used in devices such as trampolines, pogo sticks, and shock absorbers. It is also used in many mechanical systems, such as car suspensions and door hinges, to store and release energy efficiently.

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