Question Detail

If no external force acts on a system of bodies, the total linear momentum of the system of bodies remains constant. Which law states this ?

Newton first law
Newton second law
Newton third law
Principle of conservation of linear momentum

Answer: Option D

1. Which instrument is used to measure pressure of gases ?

Manometer
Machmeter
Magnetometer
Micrometer

Answer: Option A

Explanation:

Machmeter - is used to determine the speed of an aircraft in terms of speed of sound,

Magnetometer - is used to compare magnetic movements and fields,

Micrometer - is used to convert sound waves into electrical vibrations.

2. Which law states, "The rate of loss of heat by a body is directly proportional to the difference in temperature between the body and the surroundings."

Doppler's Effect
Newton's law of cooling
Kirchhoff's Law
Stefan's Law

Answer: Option B

Explanation:

Doppler's Effect - The Doppler effect can be described as the effect produced by a moving source of waves in which there is an apparent upward shift in frequency for observers towards whom the source is approaching and an apparent downward shift in frequency for observers from whom the source is receding.

Kirchhoff's Law - Kirchhoff's Law signifies that good absorbers are good emitters.

Stefan's Law - The radiant energy emitted by a black body per unit area per unit time is directly proportional to the fourth power of its absolute temperature.

3. Which instrument is used to measure sound under water ?

Hygrometer
Hygroscope
Hypsometer
Hydrophone

Answer: Option D

Explanation:

Hygrometer - is used to measure level of humidity,

Hygroscope - shows the changes in atmospheric humidity,

Hypsometer - is used to determine the boiling points of liquids.

4. What are audible sound waves ?

Having frequency less than 20 Hz
Having frequency between 20 Hz to 20000 Hz
Having frequency more than 20000 Hz
None of above

Answer: Option B

5. What is newton third law of motion ?

Every body maintains its initial state rest or motion unless no external force is applied.
The rate of change in momentum of a body is directly proportional to the applied force on the body and takes place in the direction of force.
To every action there is equal and opposite reaction.
None of above.

Answer: Option C

Explanation:

Newton First Law of Motion : Every body maintains its initial state rest or motion unless no external force is applied.

Newton Second Law of Motion : The rate of change in momentum of a body is directly proportional to the applied force on the body and takes place in the direction of force.