#neet
- ^290_82X α Y e^+ Z β^- P e^- QIn the nuclear emission stated above, the mass number and atomic number of the product Q respectively, are : Answer: 1. 286, 81 Key idea: α emission lowers A by 4 and Z by 2; β^+ (positron) lowers Z by 1; β^- (electron) raises Z by 1. The mass numbe... 1
- Two bodies A and B of same mass undergo completely inelastic one dimensional collision. The body A moves with velocity v_1 while body B is at rest before collision. The velocity of the system after collision is v_2. The ratio v_1 : v_2 is : Answer: 3. 2:1 Key idea: In a completely inelastic collision the bodies stick together and momentum is conserved. mv₁+0=(m+m)v₂ , so v₂=v₁/2... 1
- In the following circuit, the equivalent capacitance between terminal A and terminal B is : Answer: 2. 2 μ F Key idea: The circuit is symmetric, so the middle capacitor is part of a balanced bridge and holds no charge. Let M be the... 1
- A horizontal force 10 N is applied to a block A as shown in figure. The mass of blocks A and B are 2 kg and 3 kg, respectively. The blocks slide over a frictionless surface. The force exerted by block A on block B is : Answer: 4. 6 N Key idea: Both blocks move together with the same acceleration. Find it first, then use it for block B. a=F/m_A+m_B=10/2+3=2... 1
- A wheel of a bullock cart is rolling on a level road as shown in the figure below. If its linear speed is v in the direction shown, which one of the following options is correct (P and Q are any highest and lowest points on the wheel, respectively)? Answer: 3. Point P moves faster than point Q . Key idea: In pure rolling, each point has speed = (speed of centre) + (rotational speed about... 1
- The mass of a planet is 1/10th that of the earth and its diameter is half that of the earth. The acceleration due to gravity on that planet is : Answer: 1. 3.92 m s ⁻² Key idea: g=GM/R² . For the planet M_p=M/10 and R_p=R/2 , so g_p=G(M/10)/(R/2)²=4/10 g=0.4×9.8=3.92\ m s⁻² Option 1. 1
- The maximum elongation of a steel wire of 1 m length if the elastic limit of steel and its Young's modulus, respectively, are 8×10^8 N m^-2 and 2×10^11 N m^-2, is : Answer: 2. 4 mm Key idea: The largest stress the wire can bear without permanent change is the elastic limit. Use Y=stress/strain . Strain =... 1
- If the monochromatic source in Young's double slit experiment is replaced by white light, then Answer: 4. there will be a central bright white fringe surrounded by a few coloured fringes. Key idea: Each colour makes its own fringe patt... 1
- Match List I with List II.List I (Spectral Lines of Hydrogen for transitions from): A. n_2=3 to n_1=2; B. n_2=4 to n_1=2; C. n_2=5 to n_1=2; D. n_2=6 to n_1=2List II (Wavelengths (nm)): I. 410.2; II. 434.1; III. 656.3; IV. 486.1Choose the correct ans… Answer: 3. A-III, B-IV, C-II, D-I Key idea: These are Balmer lines (transitions to n=2 ); a larger jump means more energy and a shorter wave... 1
- Match List-I with List-II.List-I (Material): A. Diamagnetic; B. Ferromagnetic; C. Paramagnetic; D. Non-magneticList-II (Susceptibility ()): I. =0; II. 0>≥-1; III. 1; IV. 0<<ε (a small positive number)Choose the correct answer from the options given b… Answer: 2. A-II, B-III, C-IV, D-I Key idea: The sign and size of magnetic susceptibility chi identify the type of material. Diamagnetic: chi... 1
- In a uniform magnetic field of 0.049 T, a magnetic needle performs 20 complete oscillations in 5 seconds as shown. The moment of inertia of the needle is 9.8×10^-6 kg m^2. If the magnitude of magnetic moment of the needle is x×10^-5 Am^2; then the va… Answer: 1. 1280 π² Key idea: A magnetic needle in a field oscillates like a torsional pendulum: T=2π√(I/MB) . Period T=5/20=0.25 s. Squaring... 1
- An unpolarised light beam strikes a glass surface at Brewster's angle. Then Answer: 1. the reflected light will be completely polarised but the refracted light will be partially polarised. Key idea: At Brewster's ang... 1
- Consider the following statements A and B and identify the correct answer :A. For a solar-cell, the I-V characteristics lies in the IV quadrant of the given graph.B. In a reverse biased pn junction diode, the current measured in (μ A), is due to majo… Answer: 2. A is correct but B is incorrect. Key idea: Check each statement separately. A: A solar cell works as a generator, so its I-V curv... 1
- A light ray enters through a right angled prism at point P with the angle of incidence 30^° as shown in figure. It travels through the prism parallel to its base BC and emerges along the face AC. The refractive index of the prism is: Answer: 3. sqrt5/2 Key idea: The ray leaves along face AC, so its angle of incidence on AC is the critical angle C , with sin C=frac1μ . Let... 1
- A particle moving with uniform speed in a circular path maintains : Answer: 1. varying velocity and varying acceleration. Key idea: Velocity and acceleration are vectors, so a change in direction counts as a... 1
- The graph which shows the variation of ≤ft(1/λ^2) and its kinetic energy, E is (where λ is de Broglie wavelength of a free particle) : Answer: 1. graph (1) Key idea: For a free particle E=p²/2m and λ=h/p . So E=h²/2mλ² , which gives frac1λ²=2m/h²E . frac1λ² is directly propo... 1
- A wire of length 'l' and resistance 100 Ω is divided into 10 equal parts. The first 5 parts are connected in series while the next 5 parts are connected in parallel. The two combinations are again connected in series. The resistance of this final com… Answer: 3. 52 Ω Key idea: Each of the 10 equal parts has resistance 100/10=10\ Ω . Five parts in series: 5×10=50\ Ω . Five parts in parallel... 1
- The moment of inertia of a thin rod about an axis passing through its mid point and perpendicular to the rod is 2400 g cm^2. The length of the 400 g rod is nearly : Answer: 2. 8.5 cm Key idea: For a thin rod about its midpoint and perpendicular to its length, I=ML²/12 . L²=12I/M=12×2400/400=72 , so L=√(7... 1
- The output (Y) of the given logic gate is similar to the output of an/a : Answer: 1. AND gate Key idea: Find the output of each first-stage gate, then apply the final NOR gate. With the inputs of each gate joined,... 1
- In a vernier calipers, (N+1) divisions of vernier scale coincide with N divisions of main scale. If 1 MSD represents 0.1 mm, the vernier constant (in cm) is : Answer: 3. 1/100(N+1) Key idea: Vernier constant = 1 MSD - 1 VSD. N main scale divisions equal N+1 vernier divisions, so 1 VSD=N/N+1 MSD . V... 1
- Select the correct statements with reference to chordates.A. Presence of a mid-dorsal, solid and double nerve cord.B. Presence of closed circulatory system.C. Presence of paired pharyngeal gillslits.D. Presence of dorsal heartE. Triploblastic pseudoc… Answer: 3. B and C only Key idea: Recall the basic features of chordates. A is wrong: the nerve cord is dorsal, hollow and single. B is corr... 1
- Which of the following is characteristic feature of cockroach regarding sexual dimorphism ? Answer: 3. Presence of anal styles Key idea: In cockroaches, males have a pair of anal styles that females lack. Both sexes have anal cerci,... 1
- Given below are two statements:Statement I: During G_0 phase of cell cycle, the cell is metabolically inactive.Statement II: The centrosome undergoes duplication during S phase of interphase.In the light of the above statements, choose the most appro… Answer: 1. Statement I is incorrect but Statement II is correct. Key idea: G₀ is a quiescent stage, not a dead stage. Statement I is incorre... 1
- Which of the following are NOT under the control of thyroid hormone?A. Maintenance of water and electrolyte balanceB. Regulation of basal metabolic rateC. Normal rhythm of sleep-wake cycleD. Development of immune systemE. Support the process of R.B.C… Answer: 4. C and D only Key idea: Thyroid hormones act on metabolism, water-electrolyte balance and RBC formation. A: thyroid hormones suppo... 1