A circular platform is mounted on the frictionless vertical axle. Its radius R =2 m and its moment of inertia about the axle is 200 kg m². It is initially at rest. A 50 kg man stands on the edge of the platform and begins to walk along the edge at the speed of 1 ms^-1 relative to the ground. Time taken by the man to complete one revolution is

π sec

3π/2 sec

2π sec

π/2 sec

Solution

π sec

For conservation of angular momentum
$Iω space equals space mvr 200 space straight x space straight omega space equals space 50 space straight x space 2 space straight x space 1 space straight omega space equals space 1 half space rad divided by straight s straight v equals space rω space equals space 1 space straight m divided by straight s straight T equals space fraction numerator 2 πr over denominator 1 minus left parenthesis negative 1 right parenthesis end fraction space equals space fraction numerator 2 πr over denominator 2 end fraction space equals space πr space sec$

Some More Questions From Units and Measurement Chapter

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Units And Measurement

Some More Questions From Units and Measurement Chapter

What is the need of measurement?

Define physical quantity.

Give four examples of physical quantities.

Define unit.

What are the two main required characteristics of a unit?

Can we use same units for different physical quantities?

Can we use different units to measure same physical quantity?

To measure a physical quantity X, the unit U is repeatedly used for n times. What is the magnitude of physical quantity?

Does the numerical factor in the quantitative measurement depend on the system of unit used?

Is one unit sufficient to measure a physical quantity?

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