/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 118 A particle moves in a straight l... [FREE SOLUTION] | 91Ó°ÊÓ

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A particle moves in a straight line with retardation proportion to its displacement. Its loss of kinetic energy for any displacement \(x\) is proportional to [2004] (A) \(x\) (B) \(e^{x}\) (C) \(x^{2}\) (D) \(\log _{e} x\)

Short Answer

Expert verified
The loss of kinetic energy for any displacement \(x\) is proportional to \(x^{2}\).

Step by step solution

01

Introduce the Variables

We are given that the retardation (negative acceleration) is proportional to the displacement (\(x\)). We can express this relationship as an equation: \(a = -kx\) Where, \(a\) is the acceleration, \(k\) is a constant of proportionality and \(x\) is the displacement.
02

Introduce Newton's Second Law

Newton's second law states that force acting on a body is equal to the mass times the acceleration of the body: \(F = ma\) Since the friction (retardation) is acting against the motion, we can replace the force \((F)\) with the negative of the force \((F_{r})\), i.e., \(-F_{r} = -ma\)
03

Relate the Retardation and Displacement

Using Step 1 and Step 2 results, we have: \(-F_{r} = -m(-kx)\) \(F_{r} = mkx\) Now let's consider the work-energy theorem to calculate the work done by this force (retardation) over the displacement.
04

Apply the Work-Energy Theorem

The work-energy theorem states that the work done on an object is equal to the change in its kinetic energy: \(W = \Delta K\) In our case, work (\(W\)) is done by the retarding force, and it is equal to the loss of kinetic energy. We can express the work done by the retarding force as: \(W = \int_{x_{1}}^{x_{2}} F_{r}dx\)
05

Calculate the Loss of Kinetic Energy as a Function of Displacement

Now we can substitute the expression for retarding force from step 3 and integrate to find the relationship between the loss of kinetic energy and displacement: \(\Delta K = \int_{x_{1}}^{x_{2}} mkxdx\) \(\Delta K = mk\int_{x_{1}}^{x_{2}} xdx\) \(\Delta K = mk\Big[\frac{1}{2}x^2\Big]_{x_{1}}^{x_{2}}\) Since we are ultimately interested in the loss of kinetic energy for "any" displacement \(x\), let's take \(x_{1} = 0\) and \(x_{2} = x\). Therefore: \(\Delta K = mk\Big[\frac{1}{2}x^2\Big]_{0}^{x}\) \(\Delta K = \frac{1}{2}mkx^{2}\) We can see that the loss of kinetic energy is proportional to \(x^{2}\). Hence, the correct answer is: (C) \(x^{2}\)

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