Explanation:
- Hydroxyapatite, [Ca5(PO4)3(OH)], is present in tooth enamel.
- When fluoride ions (F−) are introduced, they replace the hydroxide ions (OH−), forming fluoroapatite:
Ca5(PO4)3(OH) + F− → Ca5(PO4)3F.
- Fluoroapatite has the molecular formula [3(Ca3(PO4)2·CaF2)], which is harder and more resistant to decay.
Final Answer: Option (1).
A body of mass 1000 kg is moving horizontally with a velocity of 6 m/s. If 200 kg extra mass is added, the final velocity (in m/s) is: