Search Previous Year Questions

Find real questions from previous competitive exam papers with answers and solutions.

Leave the keyword blank to browse saved questions for your selected exam, newest papers first. Add a keyword, year or topic to narrow the results.

Browse complete papers
Showing 10 question(s)
Clear

Question 291

National Defence Academy (NDA) 2025• General Ability Test

The focal length of a concave lens is 0.5 m. The power of the lens is 

  1. AOption (a)

    +0.5 D

  2. BOption (b)

    -0.5 D

  3. COption (c)

    +2.0 D

  4. DOption (d)

    -2.0 D

View answer & explanation

Correct answer

Answer: (d)D.

-2.0 D

Why this answer is correct

Calculation

Given focal length of the concave lens, f = −0.5 m.

Power of a lens is defined as:

P = 1 / f

Substituting the value of f,

P = 1 / (−0.5)

P = −2.0 D

The negative sign indicates that the lens is concave.

Therefore, the correct answer is Option 4.

Question 292

National Defence Academy (NDA) 2025• General Ability Test

The rule to determine the direction of a force experienced by a straight current carrying conductor placed in a magnetic field which is perpendicular to it is 

  1. AOption (a)

    Right-hand thumb rule

  2. BOption (b)

    Fleming’s left-hand rule 

  3. COption (c)

    Fleming’s right-hand rule 

  4. DOption (d)

    Hund’s rule 

View answer & explanation

Correct answer

Answer: (b)B.

Fleming’s left-hand rule 

Why this answer is correct

Calculation

This situation involves three mutually perpendicular directions:

⇒ direction of magnetic field

⇒ direction of current

⇒ direction of force (motion) on the conductor

Fleming’s left-hand rule is specifically used to determine the direction of force experienced by a current-carrying conductor in a magnetic field.

Right-hand thumb rule is used to find the direction of magnetic field due to current, not force.

Fleming’s right-hand rule applies to generators, and Hund’s rule is related to atomic structure.

Therefore, the correct answer is Option 2.

Question 293

National Defence Academy (NDA) 2025• General Ability Test

One parsec in astronomical units (A.U.) is about 

  1. AOption (a)

    2 × 103 A.U.

  2. BOption (b)

    2 × 104 A.U.

  3. COption (c)

    2 × 105 A.U.

  4. DOption (d)

    2 × 106 A.U.

View answer & explanation

Correct answer

Answer: (c)C.

2 × 105 A.U.

Why this answer is correct

Calculation

One parsec is defined as the distance at which one astronomical unit subtends an angle of one arcsecond.

Numerically,

⇒ 1 parsec ≈ 206,265 astronomical units (A.U.)

Expressing this value in scientific notation:

⇒ 206,265 ≈ 2 × 105

Hence,

⇒ 1 parsec ≈ 2 × 105 A.U.

Therefore, the correct answer is Option 3.

Question 294

National Defence Academy (NDA) 2025• General Ability Test

Which one of the following statements for second law of motion is NOT correct ? 

  1. AOption (a)

    The net force on a body is proportional to that body’s acceleration 

  2. BOption (b)

    The net force on a body is in the same direction as the acceleration 

  3. COption (c)

    The time rate of change of momentum is equal to force 

  4. DOption (d)

    The net force on a body is proportional to that body’s momentum 

View answer & explanation

Correct answer

Answer: (d)D.

The net force on a body is proportional to that body’s momentum 

Why this answer is correct

Calculation

According to the second law of motion, the net force acting on a body is related to its motion.

⇒ Force is proportional to acceleration.

⇒ Force acts in the same direction as acceleration.

⇒ Force equals the time rate of change of momentum.

Momentum is given by:

⇒ p = m × v

Hence, force depends on how momentum changes with time, not on momentum itself.

Therefore, the statement saying that force is proportional to momentum is incorrect.

Therefore, the correct answer is Option 4.

Question 295

National Defence Academy (NDA) 2025• General Ability Test

The temperature of a body increases  from 310 K to 340 K. The temperature increase in degree Celsius is 

  1. AOption (a)

    20°C 

  2. BOption (b)

    30°C 

  3. COption (c)

    37°C

  4. DOption (d)

    67°C

View answer & explanation

Correct answer

Answer: (b)B.

30°C 

Why this answer is correct

Calculation

Initial temperature, T1 = 310 K

Final temperature, T2 = 340 K

Increase in temperature = T2 − T1 ⇒ 340 − 310 = 30 K

Temperature difference remains the same in Kelvin and Celsius.

Initial temperature in Celsius ⇒ 310 − 273 = 37°C

Final temperature in Celsius ⇒ 340 − 273 = 67°C

Increase in Celsius ⇒ 67 − 37 = 30°C

Thus, the temperature increase is 30°C.

Question 296

National Defence Academy (NDA) 2025• General Ability Test

Which one of the following statements for the work done by gravity on a body is NOT correct ? 

  1. AOption (a)

    Work done is independent of the path followed by the body

  2. BOption (b)

    Work done depends only on the vertical distance separating the initial and the final position of the body 

  3. COption (c)

    Work done depends on the path followed by the body 

  4. DOption (d)

    Work done is zero if the body is displaced horizontally to the force of gravity

View answer & explanation

Correct answer

Answer: (c)C.

Work done depends on the path followed by the body 

Why this answer is correct

Calculation

Work done by gravity depends only on the vertical displacement.

Work = m × g × h

⇒ m is the mass of the body

⇒ g is acceleration due to gravity

⇒ h is the vertical distance between initial and final positions

Gravity is a conservative force.

⇒ Work done is independent of the path followed ✔

⇒ Work done depends only on vertical separation ✔

⇒ Work done does not depend on the path ✔

⇒ Work done is zero for horizontal displacement ✔

The statement saying that work done depends on the path followed is incorrect.

Therefore, the correct answer is Option 3.

Question 297

National Defence Academy (NDA) 2025• General Ability Test

Which one among the following statements is correct ? 

  1. AOption (a)

    Pressure has magnitude as well as direction: 

  2. BOption (b)

    As we go deeper in a liquid, the pressure decreases 

  3. COption (c)

    Action and reaction forces act on the same object 

  4. DOption (d)

    Pascal and N/m2 represent the same unit

View answer & explanation

Correct answer

Answer: (d)D.

Pascal and N/m2 represent the same unit

Why this answer is correct

Calculation

Pressure is a scalar quantity.

⇒ It has magnitude only, not direction.

Pressure in a liquid increases with depth.

⇒ It does not decrease as we go deeper.

According to Newton’s third law:

⇒ Action and reaction forces act on different bodies, not on the same object.

The SI unit of pressure is pascal.

⇒ 1 pascal = 1 N/m2.

Hence, the statement that pascal and N/m2 represent the same unit is correct.

Therefore, the correct answer is Option 4.

Question 298

National Defence Academy (NDA) 2025• General Ability Test

Which one of the following wavelength radiations may correspond to an X-ray ? 

  1. AOption (a)

    1 nm 

  2. BOption (b)

    10 nm

  3. COption (c)

    100 nm

  4. DOption (d)

    300 nm 

View answer & explanation

Correct answer

Answer: (a)A.

1 nm 

Why this answer is correct

Calculation

X-rays have wavelengths in the range of about 0.01 nm to 10 nm.

1 nm lies within this X-ray wavelength range.

10 nm lies at the boundary and generally falls in the ultraviolet region.

100 nm and 300 nm correspond to ultraviolet radiation, not X-rays.

Hence, among the given options, 1 nm represents X-ray radiation.

Therefore, the correct answer is Option 1.

Question 299

National Defence Academy (NDA) 2025• General Ability Test

In a Telescope, compared to the eyepiece lens the objective lens has 

  1. AOption (a)

    larger focal length and larger aperture

  2. BOption (b)

    larger focal length and smaller aperture 

  3. COption (c)

    smaller focal length and larger aperture

  4. DOption (d)

    smaller focal length and smaller aperture 

View answer & explanation

Correct answer

Answer: (a)A.

larger focal length and larger aperture

Why this answer is correct

Explanation:

In a telescope, the objective lens is meant to collect light from distant objects.

To gather sufficient light, it must have a larger aperture.

To properly focus nearly parallel rays from distant objects, it requires a larger focal length.

The eyepiece, in contrast, has a smaller focal length and smaller aperture for magnification.

⇒ Compared to the eyepiece, the objective lens has both a larger focal length and a larger aperture.

Therefore, the correct answer is Option 1.

Question 300

National Defence Academy (NDA) 2025• General Ability Test

The energy, E, of a photon can be expressed as E = hf where f is the frequency and h is Planck’s constant. The dimensions of h are the same as that of 

  1. AOption (a)

    linear momentum 

  2. BOption (b)

    angular momentum 

  3. COption (c)

    displacement 

  4. DOption (d)

    torque 

View answer & explanation

Correct answer

Answer: (b)B.

angular momentum 

Why this answer is correct

Calculation:

The energy of a photon is given by the relation E = h × f.

Here, E represents energy, f represents frequency, and h is Planck’s constant.

The dimensional formula of energy is [M L2 T−2, while the dimensional formula of frequency is [T−1].

From the relation h = E / f

⇒[h] = [M L2 T−2] / [T−1]

⇒ [h] = [M L2 T−1]

Angular momentum also has the dimensional formula [M L2 T−1], which matches that of Planck’s constant.

Therefore, the correct answer is Option 2.

Page 30