Two disks are rotating about the same axis. disk a has a moment of inertia of 3.3 kg · m2 and an angular velocity of +6.6 rad/s. disk b is rotating with an angular velocity of -9.3 rad/s. the two disks are then linked together without the aid of any external torques, so that they rotate as a single unit with an angular velocity of -2.1 rad/s. the axis of rotation for this unit is the same as that for the separate disks. what is the moment of inertia of disk b?

The angular momentum of a rotation object is the product of its moment of inertia and its angular velocity:

L = Iω

L is the angular momentum, I is the moment of inertia, and ω is the angular velocity.

Apply the conservation of angular momentum. The total angular momentum before disks A and B are joined is:

L_{before} = (3.3)(6.6) + B(-9.3)

L_{before} = -9.3B+21.78

where B is the moment of inertia of disk B.

The total angular momentum after the disks are joined is:

L_{after} = (3.3+B)(-2.1)

L_{after} = -2.1B-6.93

L_{before} = L_{after}

-9.3B + 21.78 = -2.1B - 6.93

B = 4.0kg·m²

The moment of inertia of disk B is 4.0kg·m²

answer: option c. i.e. electric current flowing “downhill” from the negative electrode to the positive electrode in a battery

explanation:

the water analogy to the circuits define the pipes (water flows) to the electric current. now, we know that the electric current flows from the positive terminal to the circuit (as shown in the diagram attached).

hence, option c is the correct answer.

.) the observation by semmelweis that more mothers died of childbed fever when their doctors also worked in the morgue