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\(\Lambda\) body of mass \(M\) is attached to the lower end of a metal wire, whose upper end is fixed. 'Ihe clongation of the wire is \(l\) (a) loss in gravitational polential cnergy of \(M\) is \(M g l\) (b) the clastic potential encrgy stored in the wirc is \(M g l\) (c) the clastic potential energy swred in the wire is \(1 / 2 M g l\) (d) heal produced is \(1 / 2 \mathrm{Mgl}\)

Short Answer

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(a) True (b) False (c) True (d) True

Step by step solution

01

Understand Energy Changes

When a mass \( M \) is hung from a wire, its gravitational potential energy decreases. The potential energy initially held by the mass (due to gravity) is converted into other forms of energy, specifically potential energy stored in the wire due to deformation and potentially heat or other losses.
02

Gravitational Potential Energy Loss

The loss in gravitational potential energy as the mass \( M \) is lowered by a distance \( l \) is calculated by \( \Delta U = M g l \). This is due to the fact that gravitational potential energy is given by \( U = mgh \).
03

Calculate Stored Elastic Potential Energy

When the wire stretches by \( l \), it stores energy as elastic potential energy. For a material obeying Hooke's law, the elastic potential energy stored is given by the work done in stretching the wire from 0 to \( l \), which is \( \frac{1}{2} k l^2 \), where \( k \) is the spring constant. However, from the principle of energy conservation, since the whole potential energy is available for storage and other transformations, this results in \( \frac{1}{2} M g l \) being stored as elastic potential energy.
04

Calculate Heat and Other Losses

The difference between the gravitational potential energy lost \( M g l \) and the elastic potential energy stored \( \frac{1}{2} M g l \) results in energy dissipated as heat or other forms of energy not stored in the wire. The remaining energy is \( \frac{1}{2} M g l \). This follows from energy conservation: initial energy = stored energy + dissipated energy.

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Key Concepts

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

Gravitational Potential Energy
Gravitational potential energy is a form of energy associated with the height of an object relative to a gravitational field, such as Earth's. When you hold an object of mass \( M \) at a height, it has gravitational potential energy because of its position. This can be calculated with the formula \( U = mgh \), where \( m \) is the mass, \( g \) is the acceleration due to gravity, and \( h \) is the height.When the mass is lowered a distance \( l \), its height decreases, causing a loss in its gravitational potential energy. This lost energy can be computed using \( \Delta U = M g l \). Here, the reduction in potential energy doesn't disappear but transitions into other forms. Understanding this transition helps illustrate the conservation of energy in actions such as raising or lowering objects.
Hooke's Law
Hooke's Law describes the behavior of springs and elastic materials when they are stretched or compressed. It states that the force required to compress or stretch a spring by some distance is proportional to that distance, which can be expressed as \( F = -kx \), where \( k \) is the spring constant, and \( x \) is the displacement from the equilibrium position.For the wire in the exercise, this principle applies when the mass stretches it. When a force like weight is applied, and the wire stretches by distance \( l \), it stores elastic potential energy. According to Hooke's Law, this stored energy, in ideal situations, could be derived from the work done by this force over the displacement. Normally, elastic energy stored would be \( \frac{1}{2} k l^2 \), but in situations described in the exercise where energy conservation is considered, the elastic energy calculation follows from how gravitational potential energy transitions into elastic potential energy.
Energy Conservation
Energy conservation is a principle stating that energy cannot be created or destroyed, only transformed from one form to another. In the context of the exercise, this means that the total initial gravitational potential energy of the mass must equal the sum of all subsequent energies (stored and dissipated).Initially, when the mass is lowered, the gravitational potential energy loss \( M g l \) is shared between the elastic potential energy stored in the wire and energy lost through heat or other non-stored means. Given the exercise conditions, elastic potential energy is calculated as \( \frac{1}{2} M g l \). Therefore, the energy dissipated as heat is also \( \frac{1}{2} M g l \), ensuring that the total transformation matches the initial potential energy lost in accordance with energy conservation principles.This balance underlines a key concept: when analyzing physical systems, tracking energy transformation helps make predictions and ensures all forms of energy are appropriately accounted for.

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