Fluoride toothpaste is sometimes recommended because fluoride: f

Subject

General Knowledge

Class

NDA Class 12

Pre Boards

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Sample Papers

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 Multiple Choice QuestionsMultiple Choice Questions

1.

Which one of the following statements is correct?

  • Covalent bonds are directional

  • Ionic bonds are directional

  • Both covalent and ionic bonds are directional

  • Both covalent and ionic bonds are non-directional


2.

When one strikes a safety match, the first step is:

  • burning of sulphur

  • decomposition of potassium chlorate into potassium chloride and oxygen

  • conversion of a small amount of red phosphorus into white phosphorus

  • burning of glue and starch


3.

The LPG cooking gas contains propane and butane as the constituents. A sulphur containing compound is added to the LPG, because:

  • it lowers the cost of production

  • it enhances the efficiency of LPG

  • it facilitates easy detection of leakage of the gas

  • it assists in liquefying hydrocarbons


4.

The genetic material of bacteria is found in:

  • nucleus

  • cytoplasm

  • cell membrane

  • ribosome


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5.

A horse and a donkey can breed to produce mule which is an infertile animal. The infertility is because horse and donkey belong to different:

  • class

  • order

  • species

  • genus


6.

A plant having yellow leaves with dead spots has the deficiency of:

  • Potassium

  • Magnesium

  • Nitrate

  • Phosphate


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7.

Fluoride toothpaste is sometimes recommended because fluoride:

  • prevents plaque formation

  • hardens the enamel of the tooth

  • kills pathogenic bacteria

  • prevents tooth ache


B.

hardens the enamel of the tooth

Fluoride therapy is the delivery of fluoride to the teeth, topically or systemically, to protect them from dental caries (cavities). Strictly speaking, fluoride therapy repairs rather than prevents damage to the teeth, causing the mineral fluorapatite to be incorporated into damaged tooth enamel.


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8.

Along a streamline flow of fluid:

  • the velocity of all fluid particles at a given instant is constant

  • the speed of a fluid particle remains constant

  • the velocity of all fluid particles crossing a given position is constant

  • the velocity of a fluid particle remains constant


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9.

How is the kinetic energy of a moving object affected if the net work done on it is positive?

  • Decreases

  • Increases

  • Remains constant

  • Becomes zero


10.

A particle is executing simple harmonic motion. Which one of the following statements about the acceleration of the oscillating particle is true?

  • It is always in the opposite direction to velocity

  • It is proportional to the frequency of oscillation

  • It is minimum when the speed is maximum

  • It decreases as the potential energy increases


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