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One end of an unstretched vertical spring is attached to the ceiling and an object attached to the other end is slowly lowered to its equilibrium position. If \(S\) is the gain in spring energy and \(G\) is the loss in gravitational potential energy in the process, then (1) \(S=G\) (2) \(S=2 G\) (3) \(G=2 S\) (4) None of these

Short Answer

Expert verified
The correct answer is (3) \( G = 2S \).

Step by step solution

01

Understand the Situation

Initially, the spring has no stored energy, and the object has a certain amount of gravitational potential energy when held before release. As the object is slowly lowered, it reaches its equilibrium position where it stretches the spring to a new length.
02

Determine Gravitational Potential Energy Loss

The loss in gravitational potential energy, \( G \), is calculated as the change from the object's initial height to its equilibrium position. Let \( x \) be the displacement of the spring from its unstretched position. Thus, \( G = mgx \), where \( m \) is the object's mass and \( g \) is the acceleration due to gravity.
03

Calculate Gain in Spring Energy

The gain in spring energy, \( S \), when the spring stretches by \( x \), is given by the formula \( S = \frac{1}{2} kx^2 \), where \( k \) is the spring constant. This represents the potential energy stored in the spring at equilibrium.
04

Equate Forces at Equilibrium

At the equilibrium position, the force due to gravity \( mg \) is balanced by the spring force \( kx \). Therefore, \( mg = kx \). Substitute \( kx = mg \) in the spring energy formula to express \( k \): \( k = \frac{mg}{x} \).
05

Relationship Between S and G

Substitute \( k = \frac{mg}{x} \) into \( S = \frac{1}{2} kx^2 \). This gives \( S = \frac{1}{2} (\frac{mg}{x}) x^2 = \frac{1}{2} mgx \). Notice that \( S = \frac{1}{2} G \), i.e., \( G = 2S \). Thus, option (3) \( G = 2S \) is correct.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Gravitational Potential Energy
When we talk about gravitational potential energy (GPE), we are referring to the energy an object possesses because of its position in a gravitational field. In simpler terms, it's the energy stored due to an object's height above the ground. The formula to calculate GPE is given as: \[ G = mgh \] where:
  • \( m \) is the mass of the object,
  • \( g \) is the acceleration due to gravity (approximately \( 9.81 \, \text{m/s}^2 \) on Earth), and
  • \( h \) is the height above the reference point or ground.
In the context of this exercise, as the object attached to the spring is slowly lowered, it loses gravitational potential energy because it moves downward, closer to the ground. This loss in energy is given by \( G = mgx \), where \( x \) is the displacement from the initial position to the equilibrium position. This formulation helps us understand how GPE is transferred into other forms of energy, such as the energy stored in the spring.
Equilibrium Position
The term "equilibrium position" in a mechanical system refers to the point where all forces are balanced. For a spring attached to an object, this is the position where the force exerted by the spring exactly counterbalances the gravitational force pulling the object downwards. At this equilibrium point, the spring force \( kx \) (where \( k \) is the spring constant and \( x \) is the stretch or compression of the spring) is equal to the gravitational force \( mg \). This can be represented mathematically as:\[ mg = kx \]This balance point is important because it indicates that no net force is acting on the object, and thus, the object remains at rest if left undisturbed. Understanding equilibrium helps us see how different energies play a role without additional external forces. It also shows how the system is stable under specific conditions, like the object remaining stationary at the equilibrium position.
Spring Constant
The spring constant, denoted by \( k \), is a measure of a spring's stiffness. It is crucial in determining how much force is needed to stretch or compress the spring by a certain distance. In the equation related to Hooke's Law:\[ F = kx \]This shows that the force \( F \) required to stretch or compress the spring a distance \( x \) is directly proportional to both \( k \) and \( x \). A larger spring constant implies a stiffer spring, needing more force for the same extension compared to a spring with a smaller constant.In our exercise, the spring constant helps relate gravitational force to the stretch in the spring using the equilibrium condition \( mg = kx \). When plugged into the potential energy equation \( S = \frac{1}{2} kx^2 \), it allows us to understand how the energy stored in the spring is influenced by its stiffness. Deciphering the spring constant is fundamental in determining how much energy the spring can store for any given displacement, hence better illustrating the relationship with the gravitational potential energy discussed earlier.

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Most popular questions from this chapter

A rope ladder of length \(L\) is attached to a balloon of mass \(M\). As the man of mass \(m\) climbs the ladder into the balloon basket, the balloon comes down by a vertical distance s. Then the increase in potential energy of man divided by the increase in potential energy of balloon is (1) \(\frac{L-s}{s}\) (2) \(\frac{L}{s}\) (3) \(\frac{s}{L-s}\) (4) \(L-s\)

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The \(\mathrm{PE}\) of a certain spring when stretched from natural length through a distance \(0.3 \mathrm{~m}\) is \(5.6 \mathrm{~J}\). Find the amount of work in joule that must be done on this spring to stretch it through an additional distance \(0.15 \mathrm{~m}\).

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