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2. A particle of mass m is subjected to a force given by F(x) = a-2bx^2. (a) Fin

ID: 2287054 • Letter: 2

Question

2. A particle of mass m is subjected to a force given by F(x) = a-2bx^2. (a) Find V(x) (b) Make sketches of F(x) and V(x) [Hint For a given function, identify the values of x that make the function zero (i.e., the roots), identify where the minima and maxima are using condition: dV(x)/dx = 0, and then evaluate the minimum and maximum values (i.e., Vmin and/or Vmax). Seminar Problem #3 should also provide some hints in regard to how this kind of problem may be tackled]. (e) Discuss the motion of the particle for different values of energy and point out any regions in which motion is: (i) bounded, unbounded, or forbidden, and (ii) places where the particle is at equilibrium (stable and unstable) .

Explanation / Answer

F=a-bx^2

Dv/dx= a-bx^2

V= ?a-bx^2 dx

V=ax-(bx3/3)

To find maxima and minima, let us put v=0

ax-(bx3/3)=0

ax= bx3/3

a=bx2/3

x=(3a/b)1/2

let us put this in the given equation of F(x).

F=a-bx^2

F=a-b(3a/b)

F=a-3a

F=-2a

Thus,

Vmin= ax-(bx3/3)= a(3a/b)1/2-(b(3a/b)3/2/3)