Question Discussion & Solution

CONCEPT:

Equilibrium of a rigid body:

• A rigid body is said to be in mechanical equilibrium if both its linear momentum and angular momentum are not changing with time, or equivalently, the body has neither linear acceleration nor angular acceleration.
• Condition for the mechanical equilibrium:
  1. The total force, i.e. the vector sum of the forces, on the rigid body is zero.
  2. The total torque, i.e. the vector sum of the torques on the rigid body is zero.

⇒ \(\rm\vec{F_1}+\vec{F_2}+...+\vec{F_n}=0\)

⇒ \(\rm \vec{τ_1}+\vec{τ_2}+...+\vec{τ_n}=0\)

• If the forces on a rigid body are acting in the 3 dimensions, then six independent conditions to be satisfied for the mechanical equilibrium of a rigid body.
• If all the forces acting on the body are coplanar, then we need only three conditions to be satisfied for mechanical equilibrium.
• A body may be in partial equilibrium, i.e., it may be in translational equilibrium and not in rotational equilibrium, or it may be in rotational equilibrium and not in translational equilibrium.

EXPLANATION:

• A rigid body is said to be in mechanical equilibrium if both its linear momentum and angular momentum are not changing with time, or equivalently, the body has neither linear acceleration nor angular acceleration.
• We know that the linear acceleration and the angular acceleration of a stationary body are zero.

A book is kept on a table:

• In this case, the book will be stationary so it is an example of the equilibrium of a body.

A ball is moving downward freely under gravity:

• We know that when a ball moves freely under gravity, then only the gravitational force will act on the ball due to which the ball accelerates downward.
• Therefore ball is moving downward freely under gravity is not an example of the equilibrium of a body.
• Hence, option 1 is correct.

Bleaching powder:

• Calcium hypochlorite is known as bleaching powder.​
• It is a pale yellowish powder having a strong smell of chlorine.
• It is soluble in cold water.
• Bleaching powder reacts with dilute acids to produce chlorine.
• When bleaching powder is treated with an excess of a dilute, all the chlorine present in it is liberated.
• It is used in bleaching clothes in the laundry due to its oxidizing property.

Formula- CaOCl₂ 

Additional Information

• Washing powder: The chemical name of washing soda is Sodium carbonate Decahydrate and the chemical formulae is Na_2​CO3​.10H_2​O.
• Baking powder: Sodium hydrogen carbonate is the chemical term for the baking powder with chemical formulae NaHCO₃.
• Soda ash: Anhydrous Sodium carbonate is known as Soda ash with chemical formulae Na₂CO₃.

Explanation:

Composting is one of the options for the treatment of solid waste. In the composting process, the organic matter breaks down under bacterial action resulting in the formation of humus like material called compost.

• Vermicomposting: It involves the use of earthworms for composting organic solid waste. It is a resourceful way to recycle your food waste into compost. It takes about 2-3 months.
• Vermicompost (worm manure) is the end-product of the breakdown of organic matter by earthworms. 
• This process of increasing the fertility of soil by earthworms is known as vermicomposting.

Hence, fertilizer produced by the earthworm is called Vermicompost.

Additional Information

Biofertilizers: 

• ​Is a substance that contains living micro-organisms that, when applied to seeds, plant surfaces, or soil, colonize the rhizosphere or the interior of the plant and promotes growth by increasing the supply or availability of primary nutrients to the host plant. 
• Biofertilizers add nutrients through the natural processes of Nitrogen fixation.
• Examples: Rhizobium, Azotobacter, Blue-green algae, Azospirilium.

Nitrogen fertilizer:

• Urea, also known as carbamide, is an organic compound with the chemical formula CO(NH₂)₂.
• This amide has two –NH₂ groups joined by a carbonyl functional group.
• Urea serves an important role in the metabolism of nitrogen-containing compounds by animals and is the main nitrogen-containing substance in the urine of mammals.
• The main function of Urea fertilizer is to provide the plants with nitrogen to promote green leafy growth and make the plants look lush.
• Urea has the highest nitrogen content of all solid nitrogenous fertilizers in common use.

A matter is something that occupies space, has shape, mass and volume. It can be categorized in the following categories:

• Solid: Solids are those, whose molecules are bounded tightly, hence the distance between them is the least.
  • The molecules are fixed in a position.
  • It has definite shape as well as mass.
  • It has a high density.
  • In this, vibration is the least because of tightly bound molecules
• Liquid: In this particles are more loosely packed as compared to solids. It can flow.
• Gas: In this, the molecules have a great space between them. It has no definite shape and volume.
• Plasma: It is an ionized gas substance that has sufficient energy to provide free electrons from molecules.

Here, all except Nohkalikai are names of different diseases while ‘Nohkalikai’ is a waterfall in India.