A hollow sphere is filled with water. It is hung by a long thread. As ...
Time period of simple pendulum
where l is effective
length. [i.e distance between centre of suspension and centre of gravity of bob]
Initially, centre of gravity is at the centre of sphere. When water leaks the centre of gravity goes down until it is half filled; then it begins to go up and finally it again goes at the centre. That is effective length first increases and then decreases. As
, so time period first increases and then decreases.
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A hollow sphere is filled with water. It is hung by a long thread. As ...
The period of oscillation of a hollow sphere filled with water and hung by a long thread will first increase and then decrease as the water flows out of a hole at the bottom.
Explanation:
When the hollow sphere is filled with water, it gains mass and therefore its moment of inertia increases. The moment of inertia is a measure of an object's resistance to changes in its rotational motion.
Initial Period of Oscillation:
Initially, when the sphere is filled with water, the period of oscillation is determined by the moment of inertia of the sphere filled with water. Let's denote this period as T1.
As Water Flows Out:
As the water flows out of the sphere through the hole at the bottom, the mass of the sphere decreases. This leads to a decrease in the moment of inertia of the sphere.
Decrease in Moment of Inertia:
As the moment of inertia decreases, the period of oscillation of the sphere also decreases. Let's denote this period as T2.
Minimum Moment of Inertia:
At a certain point, all the water has flowed out of the sphere, and the moment of inertia reaches its minimum value.
Maximum Period of Oscillation:
At this point, the period of oscillation reaches its minimum value T2.
Increasing Moment of Inertia:
After all the water has flowed out, if the sphere continues to oscillate, the period of oscillation starts to increase again. This is because as the sphere rotates, the water starts to accumulate on one side due to the centrifugal force. This accumulation of water increases the moment of inertia of the sphere, leading to an increase in the period of oscillation.
Maximum Moment of Inertia:
The moment of inertia reaches its maximum value when all the water has accumulated on one side of the sphere.
Decreasing Period of Oscillation:
As the moment of inertia decreases again, the period of oscillation starts to decrease. This continues until the water flows out of the hole, and the sphere becomes empty.
Therefore, the period of oscillation of the hollow sphere filled with water first increases and then decreases as the water flows out of the hole at the bottom.
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