Question Discussion & Solution

CONCEPT:

Force:

• The interaction which after applying on a body changes or try to changes the state of rest or state of motion is called force.
• It is denoted by F. The SI unit of force is Newton (N).

Force (F) = Mass (m) × acceleration (a)

• If more than one force is acting on a body, then the effect on the body is due to the net force.
• A stationary object on which no force is acting remains stationary.
• An object in motion continues to move with the same speed and direction when no force is acting on the object. This is Newton’s first law of motion. 

​CALCULATION:

Given:

Force = 20 N

Acceleration (a) = 2 m/s2

⇒ Force (F) = m a 

⇒ m = F/a = 20/2 = 10 kg.

So, option 4^th is correct.

An ohmmeter is an electrical instrument that measures electrical resistance. Similarly, barometer is a scientific instrument that is used to measure air pressure in a certain environment.

Given: 40 × 20 ÷ 28 - 4 + 2

The logic follows here is: 

  
By inserting codes and then using BODMAS Rule:

40 + 20 - 28 ÷ 4 × 2

= 40 + 20 - 7 × 2

= 40 + 20 - 14 

= 60 - 14

= 46

Hence, 46 is the correct answer.

The correct answer is Mercury.

Key Points

• Mercury is used in thermometers because it remains in liquid form throughout a wide range of temperatures i.e -37.89 degrees Fahrenheit to 674.06 degrees Fahrenheit.
• The mercury thermometer was invented by physicist Daniel Gabriel Fahrenheit in Amsterdam.
• Mercury has a greater coefficient of thermal expansion than alcohol. 
• A thermometer with alcohol is used to measure low temperature because its freezing point is low i.e -1170C.
• It is Impossible to measure high temperatures because it’s a low boiling point.
• The thermometer with mercury cannot be used to measure the very low temperature because its freezing point is high i.e -400C.
• Mercury is the only one in liquid state at room temperature.
• It's used in thermometers because it has a high coefficient of expansion.
• It also has a high boiling point which makes it very suitable to measure higher temperatures. 
• It has a shiny appearance and doesn't stick to the glass surface of the glass.

In alphabet group there is difference of five except ‘QU’

E + 5 → J

O + 5 → T

Q + 4 → U

 M + 5 → R