Taking into account, three isotopes of hydrogen and three isotopes of oxygen occurring in nature, how many different kinds of water molecules can we expect on the Earth?

• Six

• Nine

• Twelve

• Eighteen

Life of RBC in human blood is

• 30 days

• 60 days

• 120 days

• 15 h

The heating element in an electric iron is made of

• iron

• tungsten

• nichrome

• copper

Heat energy of an object is

• the average energy of the molecules of the object

• the total energy of the molecules of the object

• the average velocity of the molecules of the object

• the average potential energy of the molecules of the object

Which of the following changes when a particle is moving with uniform velocity?

• Speed

• Acceleration

• Velocity

• Position

When a body falls freely

• its PE is converted into KE

• its KE is converted into PE

• its mechanical energy is converted into heat energy

• None of the above

Rocket works on the principle of conservation of

• mass

• energy

• momentum

• None of these

Wisdom teeth normally grow during the age of

• 12-15 yr

• 17-30 yr

• 34-40 yr

• 40-45 yr

The momentum of a heavy object at rest will be

• zero

• small

• large

• None of these

Which one of the following acids is present in Vitamin C?

• Citric acid

• Ascorbic acid

• Lactic acid

• Folic acid