An annular disk of mass M , inner radius a and outer radius b is placed on a horizontal surface with…

An annular disk of mass M, inner radius a and outer radius b is placed on a horizontal surface with coefficient of friction μ, as shown in the figure. At some time, an impulse J0x is applied at a height h above the center of the disk. If h=hm then the disk rolls without slipping along the x-axis. Which of the following statement(s) is(are) correct?

  1. For μ0 and a0, hm=b2
  2. For μ0 and ab, hm=b
  3. For h=hm, the initial angular velocity does not depend on the inner radius a
  4. For μ=0 and h=0, the wheel always slides without rolling

Solution

As we know, J=P

 J0=MV              ... i

About center of the disk, we can also write

J0×h=ICMω J0×h=M2a2+b2ω              ... ii

If h=hmω=Vbpure rolling

From equation(ii), we can write

 J0×hm=M2a2+b2Vb          ... iii

By dividing equation (i) with the equation (iii), we get

 hm=a2+b22b

Now, considering all cases:

If a0hm=b2

If abhm=b

If h=hmω is independent of a(As we get ω=Vb)

If μ=0 and h=0Wheel will slide without rolling.

Asked in: JEE Advanced 2023 (Paper 2)

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