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Units and Measurement
Question
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A body at rest explodes in three fragments. What is the velocity of the centre of mass of exploded part?

Answer

Zero.
In the absence of external force, the centre of mass moves with constant velocity. Since before explosion the body was at rest, therefore, the velocity of the centre of mass is zero before an explosion. Hence it will also be zero after the explosion.

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Some More Questions From Units and Measurement Chapter

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?