Physics

posted by .

a circular disc rotates on a thin air film with a period of 0.3s. its moment of inertia about its axis of rotation is 0.06kgm^2. a small mass is dropped onto th disc and rotates with it . the moment of inertia of the mass about the axis of rotation is 0.04kgm^2.determine the final period of rotating the disc and mass?

  • Physics -

    The answer depends upon where the mass is dropped, but since they tell you the moment of inertia of the dropped mass about the axis, that is enough to answer the question.

    Angular momentum about the axis is conserved. The original angular velocity of the disc is
    w1 = 2 pi/(period1) = 20.9 rad/s
    Period is inversely proportional to angyualr velocity

    If w2 is the final angular velocity,
    I1*w1 = (I1 + I2)*w2
    w2 = (0.06/0/10)*w1 = (3/5)*w1
    Period2 = (5/3)*w1 = 0.5 seconds

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. physics

    a circular disc rotates on a thin air film with a period of 0.3s. its moment of inertia about its axis of rotation is 0.06kgm^2. a small mass is dropped onto th disc and rotates with it . the moment of inertia of the mass about the …
  2. Physics

    A student puts on a Dresden Dolls disc in her cd player which spins at 1800 revolutions per minute. A compact disc has a mass of about 0.016 kg and a radius of 6.0 cm. a) What is the period of rotation in seconds?
  3. Physics

    A student puts on a Dresden Dolls disc in her cd player which spins at 1800 revolutions per minute. A compact disc has a mass of about 0.016 kg and a radius of 6.0 cm. a) What is the period of rotation in seconds?
  4. physics

    A student puts on a Dresden Dolls disc in her cd player which spins at 1800 revolutions per minute. A compact disc has a mass of about 0.016 kg and a radius of 6.0 cm. a) What is the period of rotation in seconds?
  5. physics

    a disc of radius 5.70 cm rotates about its axis and a point 1.90 cm from the center of the disc moves 34.5 cm in 12.2 s .calculate the angular velocity of the disc.
  6. physics

    a disc of radius 5.70 cm rotates about its axis and a point 1.90 cm from the center of the disc moves 34.5 cm in 12.2 s .calculate the angular velocity of the disc.
  7. physics

    from a disk of radius R,a concentric circular portion of radius r is cut out so as to leave an annular disc of mass M . the moment of inertia of this annular disc about the axis perpendicular to its plane and passing through its centre …
  8. Physics

    Consider a rod plus disc system. The rod has a total length L =1.30 m, while the disc has a radius of R = L/2. The pivot is at P where the distance between P and the end of the rod is L/4. Point O is at the center of the disc, and …
  9. Physics

    Consider the rods plus disc system shown in the Figure. The rod has a length L =0.50 m, and mass M = 0.270kg. The large disc has a radius of R = 0.130m and mass m=0.810kg. The second disk should be treated as a point mass of 0.405kg. …
  10. Physics (EMI)

    A metal disc of radius R rotates with angular velocity Omega (w) about an axis perpendicular to its plane passing through its centre in a magnetic field B acting perpendicular to the plane of the disc calculate the induced EMF between …

More Similar Questions