NEET 2016 Previous Year Question Paper

1. A 2 kg block moving at 3 m/s strikes a 1 kg block at rest and the two stick together. What is the kinetic energy of the combined body just after the collision?

   1. 9 J
   2. 6 J
   3. 3 J
   4. 4.5 J
   Answer and explanation

   Answer: B (6 J)

   Momentum is conserved: 2 × 3 = 3 × v, so v = 2 m/s. KE = ½ × 3 × 2² = 6 J (the remaining 3 J of the initial 9 J is lost in the perfectly inelastic collision).

2. A ball is projected at 20 m/s at 30° above the horizontal (g = 10 m/s²). Its maximum height is

   1. 20 m
   2. 5 m
   3. 10 m
   4. 15 m
   Answer and explanation

   Answer: B (5 m)

   H = u² sin²θ / 2g = (400 × 0.25) / 20 = 5 m.

3. A 3 Ω and a 6 Ω resistor are connected in parallel, and the combination is in series with a 4 Ω resistor across an ideal 12 V battery. The current drawn from the battery is

   1. 1 A
   2. 2 A
   3. 3 A
   4. 4 A
   Answer and explanation

   Answer: B (2 A)

   3 Ω ∥ 6 Ω = 18/9 = 2 Ω. Total resistance = 2 + 4 = 6 Ω, so I = 12/6 = 2 A.

4. Light of photon energy 4.0 eV falls on a metal of work function 2.5 eV. The stopping potential is

   1. 4.0 V
   2. 6.5 V
   3. 2.5 V
   4. 1.5 V
   Answer and explanation

   Answer: D (1.5 V)

   Kmax = hν − φ = 4.0 − 2.5 = 1.5 eV, so the stopping potential is 1.5 V.

5. A Carnot engine works between 527 °C and 127 °C. Its efficiency is

   1. 50%
   2. 76%
   3. 25%
   4. 40%
   Answer and explanation

   Answer: A (50%)

   T1 = 800 K, T2 = 400 K. η = 1 − T2/T1 = 1 − 400/800 = 0.5 = 50%.

6. The length of a simple pendulum is increased by 44%. Its time period increases by

   1. 10%
   2. 20%
   3. 22%
   4. 44%
   Answer and explanation

   Answer: B (20%)

   T ∝ √L. New T/old T = √1.44 = 1.2, i.e. an increase of 20%.

7. A first-order reaction has rate constant 6.93 × 10⁻³ s⁻¹. Its half-life is

   1. 693 s
   2. 100 s
   3. 10 s
   4. 1000 s
   Answer and explanation

   Answer: B (100 s)

   For first order, t½ = 0.693/k = 0.693 / (6.93 × 10⁻³) = 100 s.

8. Which of the following has the highest first ionisation enthalpy?

   1. O
   2. C
   3. N
   4. B
   Answer and explanation

   Answer: C (N)

   Ionisation enthalpy rises across period 2, but O is lower than N because N has a stable half-filled 2p³ configuration. Order: N > O > C > B.

9. The hybridisation of sulphur in SF₆ is

   1. sp³d²
   2. sp³
   3. dsp²
   4. sp³d
   Answer and explanation

   Answer: A (sp³d²)

   S forms six bonding pairs with no lone pair: six hybrid orbitals → sp³d², octahedral shape.

10. The IUPAC name of (CH₃)₂CH–CH₂–OH is

    1. 2-methylpropan-1-ol
    2. butan-2-ol
    3. 2-methylpropan-2-ol
    4. butan-1-ol
    Answer and explanation

    Answer: A (2-methylpropan-1-ol)

    Longest chain containing the C bearing OH has 3 carbons (propan-1-ol) with a methyl on C-2: 2-methylpropan-1-ol (isobutyl alcohol).

11. The pH of 0.001 M aqueous HCl at 25 °C is

    1. 1
    2. 11
    3. 3
    4. 2
    Answer and explanation

    Answer: C (3)

    HCl is a strong acid: [H⁺] = 10⁻³ M, so pH = −log 10⁻³ = 3.

12. Which of the following is the strongest base in aqueous solution?

    1. Methylamine
    2. Dimethylamine
    3. Aniline
    4. Ammonia
    Answer and explanation

    Answer: B (Dimethylamine)

    In water, the secondary amine (CH₃)₂NH is most basic (pKb ≈ 3.27) because of +I effect plus good solvation of its cation; CH₃NH₂ (3.38) > NH₃ (4.75) > aniline (9.38, lone pair delocalised into the ring).

Botany

13. The light reactions of photosynthesis take place in the

    1. stroma
    2. thylakoid membranes
    3. cytoplasm
    4. outer chloroplast membrane
    Answer and explanation

    Answer: B (thylakoid membranes)

    Pigment systems PS I and PS II, the electron transport chain and ATP synthase are located in the thylakoid membranes; the Calvin cycle runs in the stroma.

14. To fix one molecule of CO₂ in the Calvin cycle, the requirement of ATP and NADPH is

    1. 3 ATP and 3 NADPH
    2. 3 ATP and 2 NADPH
    3. 2 ATP and 2 NADPH
    4. 2 ATP and 3 NADPH
    Answer and explanation

    Answer: B (3 ATP and 2 NADPH)

    Per CO₂: 2 ATP and 2 NADPH for reduction of 3-PGA plus 1 ATP for regenerating RuBP = 3 ATP and 2 NADPH (18 ATP and 12 NADPH per glucose).

15. The phenotypic ratio in the F₂ generation of Mendel's dihybrid cross is

    1. 1 : 2 : 1
    2. 9 : 3 : 3 : 1
    3. 1 : 1 : 1 : 1
    4. 3 : 1
    Answer and explanation

    Answer: B (9 : 3 : 3 : 1)

    Two independently assorting genes each giving 3 : 1 combine as (3 : 1)² = 9 : 3 : 3 : 1.

16. Which of the following is a C₄ plant?

    1. Potato
    2. Rice
    3. Maize
    4. Wheat
    Answer and explanation

    Answer: C (Maize)

    Maize (like sugarcane and sorghum) shows Kranz anatomy and the Hatch–Slack pathway; wheat, rice and potato are C₃ plants.

17. The ploidy of the endosperm in a typical angiosperm is

    1. 3n
    2. n
    3. 2n
    4. 4n
    Answer and explanation

    Answer: A (3n)

    The endosperm forms when one male gamete (n) fuses with the two polar nuclei (n + n) in triple fusion, giving a triploid (3n) primary endosperm nucleus.

18. Bolting (rapid internode elongation just before flowering) in rosette plants such as cabbage is promoted by

    1. ethylene
    2. gibberellin
    3. auxin
    4. abscisic acid
    Answer and explanation

    Answer: B (gibberellin)

    Gibberellins cause internode elongation; applying GA to rosette plants like cabbage and beet induces bolting.

Zoology

19. The volume of air inspired or expired during a normal breath (tidal volume) in a healthy adult is about

    1. 3000 mL
    2. 500 mL
    3. 1200 mL
    4. 150 mL
    Answer and explanation

    Answer: B (500 mL)

    Tidal volume is about 500 mL; i.e. a healthy person breathes about 6000–8000 mL per minute.

20. Insulin is secreted by which cells of the islets of Langerhans?

    1. β-cells
    2. α-cells
    3. δ-cells
    4. PP-cells
    Answer and explanation

    Answer: A (β-cells)

    β-cells secrete insulin; α-cells secrete glucagon; δ-cells secrete somatostatin.

21. A person with which blood group can donate blood to people of any ABO group?

    1. B
    2. AB
    3. O
    4. A
    Answer and explanation

    Answer: C (O)

    Group O red cells carry neither A nor B antigen, so they are not agglutinated by anti-A or anti-B antibodies of the recipient (universal donor).

22. During contraction of a skeletal muscle fibre, the length of which band remains unchanged?

    1. A-band
    2. I-band
    3. H-zone
    4. Sarcomere
    Answer and explanation

    Answer: A (A-band)

    Thin filaments slide over thick filaments; the A-band (length of thick filaments) stays constant while the I-band and H-zone shorten.

23. Which of the following sexually transmitted infections is caused by a bacterium?

    1. Genital herpes
    2. Hepatitis B
    3. Genital warts
    4. Syphilis
    Answer and explanation

    Answer: D (Syphilis)

    Syphilis is caused by the bacterium Treponema pallidum; herpes, hepatitis B and genital warts (HPV) are viral.

24. A woman who is a carrier of haemophilia marries a normal man. What fraction of their sons is expected to be haemophilic?

    1. One-half
    2. None
    3. One-quarter
    4. All
    Answer and explanation

    Answer: A (One-half)

    Mother XᴴXʰ, father XᴴY. Sons get Y from the father and either Xᴴ or Xʰ from the mother with equal chance, so ½ of the sons are haemophilic.