Explanation

Sense organs like eyes, ears, nose, skin, and tongue detect different stimuli.

They send signals to the brain, enabling us to perceive the environment.

Explanation

The head of a chlorophyll molecule contains a porphyrin ring with a central magnesium (Mg) atom.

This ring has four nitrogen atoms that coordinate with the magnesium, forming a stable complex essential for photosynthesis.

Explanation

In HNO₃ (nitric acid):

Hydrogen (H) = +1

Oxygen (O) = -2 (×3 = -6)

Let nitrogen = x

So, +1 + x + (−6) = 0

⇒ x = +5

Nitrogen has an oxidation state of +5 in HNO₃.

Explanation

Terrestrial planets are rocky planets, including Earth, Mars, Venus, and Mercury.

These planets have solid, rocky surfaces.

Unlike gas giants which are composed mainly of gases.

Explanation

Ozone (O₃) is a triatomic molecule of oxygen, not a noble (rare) gas.

Radon, Xenon, and Krypton are all noble gases found in Group 18 of the periodic table.

Explanation

Diamond is a non-metal with a high-density.

Graphite: A non-metal but has a lower density (~2.2 g/cm³).

Hydrogen: The lightest element with very low density (~0.000089 g/cm³).

Helium: Also very low density (~0.00018 g/cm³).

Diamond: A non-metal form of carbon with high density (~3.5 g/cm³).

Iron: A metal, so not a valid choice for a non-metal category.

Explanation

The cochlea contains the vestibular system, including the semicircular canals, which help maintain balance.

It detects head movements and sends signals to the brain for coordination and posture control.

Explanation

Children aged 12 to 14 years typically need 2000–2400 calories daily, depending on gender and activity level.

This supports their growth, development, and energy needs.

Explanation

Gravitational force (F) is given by:

F ∝ (m1 * m2) / r²

If both masses (m1 and m2) are halved:

New force F' ∝ ((m1/2) * (m2/2)) / r²

F' ∝ (m1 * m2) / (4 * r²)

F' = F / 4

The gravitational force becomes one fourth.

Explanation

Work done (W) is calculated as:

W = F * d * cos(θ)

where F is the force, d is the displacement, and θ is the angle between the force and displacement.

For work done to be zero, cos(θ) needs to be 0, which happens when:

θ = 90°