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Let $P_1: y = 4x^2$ and $P_2: y = x^2 + 27$ be two parabolas. If the area of the bounded region enclosed between $P_1$ and $P_2$ is six times the area of the bounded region enclosed between the line $y = \alpha x, \alpha > 0$ and $P_1$ then $\alpha$ is equal to:

Check Answer

Correct Answer: (D) 12

Explanation

Formula

Power (P) = 1 / f

Step-by-Step Derivation

  1. The equations of the parabolas are $P_1: y = 4x^2$ and $P_2: y = x^2 + 27$.
  2. First, find the points of intersection of $P_1$ and $P_2$:
  3. $$ 4x^2 = x^2 + 27 \implies 3x^2 = 27 \implies x^2 = 9 \implies x = \pm 3 $$
  4. The area $A_1$ enclosed by $P_1$ and $P_2$ is:
  5. $$ A_1 = \int_{-3}^{3} (x^2 + 27 - 4x^2) \, dx = 2 \int_{0}^{3} (27 - 3x^2) \, dx $$
  6. $$ A_1 = 2 \left[ 27x - x^3 \right]_{0}^{3} = 2(81 - 27) = 108 $$
  7. Next, find the points of intersection of $P_1$ and the line $y = \alpha x$:
  8. $$ 4x^2 = \alpha x \implies x = 0 \text{ or } x = \frac{\alpha}{4} $$
  9. The area $A_2$ enclosed by $P_1$ and $y = \alpha x$ is:
  10. $$ A_2 = \int_{0}^{\alpha/4} (\alpha x - 4x^2) \, dx = \left[ \alpha \frac{x^2}{2} - \frac{4x^3}{3} \right]_{0}^{\alpha/4} $$
  11. $$ A_2 = \alpha \left( \frac{\alpha^2}{32} \right) - \frac{4}{3} \left( \frac{\alpha^3}{64} \right) = \frac{\alpha^3}{32} - \frac{\alpha^3}{48} = \frac{\alpha^3}{96} $$
  12. We are given that $A_1 = 6 A_2$:
  13. $$ 108 = 6 \left( \frac{\alpha^3}{96} \right) \implies 18 = \frac{\alpha^3}{96} \implies \alpha^3 = 1728 $$
  14. Taking the cube root, we get $\alpha = 12$.

Final Answer

Therefore, the power of the lens is -2.0D (Option D).

Which of the following is a scalar quantity?

Check Answer

Correct Answer: (D) Electric Current

Explanation

Electric current has both magnitude and direction (flow of charges), but it does not obey the laws of vector addition. Hence, current is considered a scalar quantity.

What is the chemical formula of common rust?

Check Answer

Correct Answer: (A) Fe₂O₃ · xH₂O

Explanation

Rust is a hydrated iron(III) oxide with the formula Fe₂O₃ · xH₂O, formed by the reaction of iron, oxygen, and water.

The time period (T) of a simple pendulum is calculated using the formula:

Check Answer

Correct Answer: (A) T = 2π √(l/g)

Explanation

Pendulum Formula

T = 2π √(l / g)

Where:

  • T = Time period (s)
  • l = length of string (m)
  • g = acceleration due to gravity (m/s²)

The formula holds true under small angular displacements.

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Let $P_1: y = 4x^2$ and $P_2: y = x^2 + 27$ be two parabolas. If the area of the bounded region enclosed between $P_1$ and $P_2$ is six times the area of the bounded region enclosed between the line $y = \alpha x, \alpha > 0$ and $P_1$ then $\alpha$ is equal to:

Check Answer

Correct Answer: (D) 12

Explanation

Formula

Power (P) = 1 / f

Step-by-Step Derivation

  1. The equations of the parabolas are $P_1: y = 4x^2$ and $P_2: y = x^2 + 27$.
  2. First, find the points of intersection of $P_1$ and $P_2$:
  3. $$ 4x^2 = x^2 + 27 \implies 3x^2 = 27 \implies x^2 = 9 \implies x = \pm 3 $$
  4. The area $A_1$ enclosed by $P_1$ and $P_2$ is:
  5. $$ A_1 = \int_{-3}^{3} (x^2 + 27 - 4x^2) \, dx = 2 \int_{0}^{3} (27 - 3x^2) \, dx $$
  6. $$ A_1 = 2 \left[ 27x - x^3 \right]_{0}^{3} = 2(81 - 27) = 108 $$
  7. Next, find the points of intersection of $P_1$ and the line $y = \alpha x$:
  8. $$ 4x^2 = \alpha x \implies x = 0 \text{ or } x = \frac{\alpha}{4} $$
  9. The area $A_2$ enclosed by $P_1$ and $y = \alpha x$ is:
  10. $$ A_2 = \int_{0}^{\alpha/4} (\alpha x - 4x^2) \, dx = \left[ \alpha \frac{x^2}{2} - \frac{4x^3}{3} \right]_{0}^{\alpha/4} $$
  11. $$ A_2 = \alpha \left( \frac{\alpha^2}{32} \right) - \frac{4}{3} \left( \frac{\alpha^3}{64} \right) = \frac{\alpha^3}{32} - \frac{\alpha^3}{48} = \frac{\alpha^3}{96} $$
  12. We are given that $A_1 = 6 A_2$:
  13. $$ 108 = 6 \left( \frac{\alpha^3}{96} \right) \implies 18 = \frac{\alpha^3}{96} \implies \alpha^3 = 1728 $$
  14. Taking the cube root, we get $\alpha = 12$.

Final Answer

Therefore, the power of the lens is -2.0D (Option D).

Which of the following is a scalar quantity?

Check Answer

Correct Answer: (D) Electric Current

Explanation

Electric current has both magnitude and direction (flow of charges), but it does not obey the laws of vector addition. Hence, current is considered a scalar quantity.

What is the chemical formula of common rust?

Check Answer

Correct Answer: (A) Fe₂O₃ · xH₂O

Explanation

Rust is a hydrated iron(III) oxide with the formula Fe₂O₃ · xH₂O, formed by the reaction of iron, oxygen, and water.

The time period (T) of a simple pendulum is calculated using the formula:

Check Answer

Correct Answer: (A) T = 2π √(l/g)

Explanation

Pendulum Formula

T = 2π √(l / g)

Where:

  • T = Time period (s)
  • l = length of string (m)
  • g = acceleration due to gravity (m/s²)

The formula holds true under small angular displacements.

A body of mass 5 kg is moving with a velocity of 10 m/s. A force is applied to it so that in 25 seconds, it attains a velocity of 35 m/s. What is the force applied?

Check Answer

Correct Answer: (B) 5 N

Explanation

Acceleration $a = \frac{v - u}{t} = \frac{35 - 10}{25} = 1 \text{ m/s}^2$.

Force $F = ma = 5 \times 1 = 5 \text{ N}$.

The work done in moving a charge of 2 C across two points having a potential difference of 12 V is:

Check Answer

Correct Answer: (B) 24 J

Explanation

Work done $W = qV = 2 \times 12 = 24 \text{ J}$.

This is the energy transferred when a charge moves through a potential difference.

What is the atomic number of an element whose electronic configuration is $2, 8, 7$?

Check Answer

Correct Answer: (C) 17

Explanation

Total electrons $= 2 + 8 + 7 = 17$. The element is Chlorine (Cl).

It belongs to Group 17 (halogens) and has 7 valence electrons, making it highly electronegative.

If $\sin\theta = \dfrac{3}{5}$, then the value of $\cos\theta$ is:

Check Answer

Correct Answer: (A) 4/5

Explanation

$\cos^2\theta = 1 - \sin^2\theta = 1 - \frac{9}{25} = \frac{16}{25}$

$\cos\theta = \frac{4}{5}$ (taking positive value for acute angle).

The pH of a neutral solution at 25°C is:

Check Answer

Correct Answer: (B) 7

Explanation

A neutral solution has equal concentrations of $\text{H}^+$ and $\text{OH}^-$ ions.

At 25°C, $[\text{H}^+] = 10^{-7}$ M, so pH $= -\log(10^{-7}) = 7$.

The acceleration due to gravity on the surface of the Moon is approximately:

Check Answer

Correct Answer: (C) 1.6 m/s²

Explanation

The Moon's gravitational acceleration is about $\frac{1}{6}$th of Earth's.

$g_{\text{moon}} \approx \frac{9.8}{6} \approx 1.63 \text{ m/s}^2 \approx 1.6 \text{ m/s}^2$.

The powerhouse of the cell is:

Check Answer

Correct Answer: (C) Mitochondria

Explanation

Mitochondria are called the "powerhouse of the cell" because they generate most of the cell's supply of adenosine triphosphate (ATP), used as a source of chemical energy.

They perform oxidative phosphorylation through the electron transport chain located in their inner membrane.

If $f(x) = x^3 - 3x^2 + 2$, then $f'(1)$ is equal to:

Check Answer

Correct Answer: (B) -3

Explanation

$f'(x) = 3x^2 - 6x$

$f'(1) = 3(1)^2 - 6(1) = 3 - 6 = -3$.

The SI unit of electric current is:

Check Answer

Correct Answer: (D) Ampere

Explanation

The Ampere (A) is the SI base unit of electric current, named after André-Marie Ampère.

1 Ampere = 1 Coulomb of charge flowing per second. Volt is the unit of potential difference, Coulomb is the unit of charge, and Ohm is the unit of resistance.

Which planet in our solar system has the most number of natural satellites (moons)?

Check Answer

Correct Answer: (B) Saturn

Explanation

Saturn has the most confirmed natural satellites of any planet in our solar system, surpassing Jupiter with over 140 known moons as of recent surveys.

Its largest moon, Titan, is the only moon in the solar system with a dense atmosphere.