NEET Prep

NEET 2019

139 questions from the 2019 paper. A sample is shown below with full explanations.

p-Block Elements 6Cell — The Unit of Life 5Molecular Basis of Inheritance 5Optics 5Principles of Inheritance and Variation 5Properties of Bulk Matter 5Evolution 4Human Health and Disease 4Microbes in Human Welfare 4Biodiversity and Conservation 3Biological Classification 3Biotechnology — Principles and Processes 3Chemical Coordination and Integration 3Equilibrium 3Plant Kingdom 3Reproductive Health 3Sexual Reproduction in Flowering Plants 3Anatomy of Flowering Plants 2Animal Kingdom 2Atoms and Nuclei 2Biomolecules (Biology) 2Biotechnology and its Applications 2Body Fluids and Circulation 2Breathing and Exchange of Gases 2Cell Cycle and Cell Division 2Chemical Bonding and Molecular Structure 2Chemical Thermodynamics 2Ecosystem 2Electrochemistry 2Electrostatics 2Excretory Products and their Elimination 2Gravitation 2Human Reproduction 2Kinematics 2Locomotion and Movement 2Magnetic Effects of Current and Magnetism 2Neural Control and Coordination 2Plant Growth and Development 2Respiration in Plants 2System of Particles and Rotational Motion 2Solutions 2Structural Organisation in Animals 2Structure of Atom 2Work 2Amines 1Some Basic Concepts of Chemistry 1Biomolecules (Chemistry) 1Chemical Kinetics 1Coordination Compounds 1Current Electricity 1d- and f-Block Elements 1Dual Nature of Matter and Radiation 1Electromagnetic Induction and AC 1Electromagnetic Waves 1Electronic Devices 1Kinetic Theory of Gases 1Laws of Motion 1Morphology of Flowering Plants 1Oscillations and Waves 1Classification of Elements and Periodicity 1The Living World 1Thermodynamics 1
Properties of Bulk Matter2019medium

Q1.When a block of mass M is suspended by a long wire of length L, the length of the wire becomes (L + l). The elastic potential energy stored in the extended wire is:

  • AMgl
  • BMgL
  • C½ MglAnswer
  • D½ MgL

Explanation

The stretching force grows linearly from zero to Mg as the wire extends, so the energy stored is the area under the force-extension line, not force times extension. Elastic potential energy = ½ × (maximum force) × (extension) = ½ Mgl. The extension is l, the extra length, not the original length L, which is why MgL and ½ MgL are wrong. Mgl is the work done by gravity; half of it is stored in the wire.

Source: NEET 2019 (5 May), Code P1, Q1

Laws of Motion2019easy

Q2.A mass m is attached to a thin wire and whirled in a vertical circle. The wire is most likely to break when:

  • Athe mass is at the highest point
  • Bthe wire is horizontal
  • Cthe mass is at the lowest pointAnswer
  • Dinclined at an angle of 60° from vertical

Explanation

At every point the tension must supply the centripetal force and also balance the component of weight along the wire. At the lowest point the two act oppositely, so T − mg = mv²/r and T = mg + mv²/r. At the top the weight helps provide the centripetal force, so T = mv²/r − mg, which is least. The speed is also greatest at the bottom by energy conservation, so both terms peak together there and that is where the wire breaks.

Source: NEET 2019 (5 May), Code P1, Q2

Magnetic Effects of Current and Magnetism2019medium

Q3.Ionized hydrogen atoms and α-particles with same momenta enter perpendicular to a constant magnetic field B. The ratio of the radii of their paths r_H : r_α will be:

  • A2 : 1Answer
  • B1 : 2
  • C4 : 1
  • D1 : 4

Explanation

For a charge moving perpendicular to a magnetic field the radius is r = p/(qB). With momentum and field the same for both, r depends only on charge: r ∝ 1/q. An ionized hydrogen atom is a proton of charge +e; an α-particle carries +2e. So r_H : r_α = (1/e) : (1/2e) = 2 : 1. Mass never enters, because it is momentum rather than speed that is held fixed here.

Source: NEET 2019 (5 May), Code P1, Q3

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Questions are reformatted from NEET previous year papers with original explanations and topic tagging. NEET Prep is not affiliated with the NEET examining body.