Practice Questions

Q60.When the current changes from +2 A to −2 A in 0.05 second, an e.m.f. of 8 V is induced in a coil. The coefficient of self-induction of the coil is (1) 0.2H (2) 0.4H (3) 0.8H (4) 0.1H

Q61.In an oscillating LC circuit the maximum charge on the capacitor is Q. The charge on the capacitor when the energy is stored equally between the electric and magnetic field is (1) Q (2) Q 2 √3 (3) Q (4) Q √2

Q67.Two identical photocathodes receive light of frequencies f1 and f2 . If the velocities of the photo electrons (of mass m ) coming out are respectively v1 and v2 , then (1) v21 −v22 = 2hm (f1 −f2) (2) v1 + v2 = [ 2hm (f1 + f2)] 1/2 (3) v21 + v22 = 2hm (f1 + f2) (4) v1 −v2 = [ 2hm (f1 −f2)] 1/2

Q85.The radionucleide 23490 Th undergoes two successive β-decays followed by one α-decay. The atomic number and the mass number respectively of the resulting radionucleide are (1) 94 and 230 (2) 90 and 230 (3) 92 and 230 (4) 92 and 234

Q86.According to the Periodic Law of elements, the variation in properties of elements is related to their (1) nuclear masses (2) atomic numbers (3) nuclear neutron-proton number ratios (4) atomic masses

Q1. Two forces are such that the sum of their magnitudes is 18 N and their resultant is 12 N which is perpendicular to the smaller force. Then the magnitudes of the forces are (1) 12 N, 6 N (2) 13 N, 5 N (3) 10 N, 8 N (4) 16 N, 2 N

Q2. Identify the pair whose dimensions are equal (1) torque and work (2) stress and energy (3) force and stress (4) force and work

Q3. From a building two balls A and B are thrown such that A is thrown upwards A and B downwards (both vertically). If vA and vB are their respective velocities on reaching the ground, then (1) VB > VA (2) VA = VB (3) VA > VB (4) their velocities depend on their masses

Q4. If a body looses half of its velocity on penetrating 3 cm in a wooden block, then how much will it penetrate more before coming to rest? (1) 1 cm (2) 2 cm (3) 3 cm (4) 4 cm

Q5. Speeds of two identical cars are u and 4u at the specific instant. The ratio of the respective distances in which the two cars are stopped from that instant is (1) 1 : 1 (2) 1 : 4 (3) 1 : 8 (4) 1 : 16

Q6. The minimum velocity (in ms−1 ) with which a car driver must traverse a flat curve of radius 150 m and coefficient of friction 0.6 to avoid skidding is (1) 60 (2) 30 (3) 15 (4) 25

Q7. A lift is moving down with acceleration a. A man in the lift drops a ball inside the lift. The acceleration of the ball as observed by the man in the lift and a man standing stationary on the ground are respectively (1) g, g (2) g - a, g - a (3) g - a, g (4) a, g

Q8. When forces F1, F2, F3 are acting on a particle of mass m such that F2 and F3 are mutually perpendicular, then the particle remains stationary. If the force F1 is now removed then the acceleration of the particle is (1) F1/m (2) F2 F3/mF1 (3) (F2 −F3)/m (4) F2/m

Q9. A light string passing over a smooth light pulley connects two blocks of masses m1 and m2 (vertically). If the acceleration of the system is g/8, then the ratio of the masses is (1) 8 : 1 (2) 9 : 7 (3) 4 : 3 (4) 5 : 3

Q10.Three identical blocks of masses m = 2 kg are drawn by a force F = 10.2 N with an acceleration of 0.6 ms−2 on a frictions surface, then what is the tension (in N ) in the string between the blocks B and C ? JEE Main 2002 JEE Main Previous Year Paper (1) 9.2 (2) 7.8 (3) 4 (4) 9.8

Q11.One end of a massless rope, which passes over a massless and frictionless pulley P is tied to a hook C while the other end is free. Maximum tension that the rope can bear is 360 N. With what value of maximum safe acceleration (in ms−2 ) can a man of 60 kg climb on the rope? (1) 16 (2) 6 (3) 4 (4) 8

Q12.A bead of weight w can slide on smooth circular wire in a vertical plane. The bead is attached by a light thread to the highest point of the wire and in equilibrium, the thread is taut and make an angle θ with the vertical then tension of the thread and reaction of the wire on the bead are (1) T = w cos θ R = w tan θ (2) T = 2w cos θ R = w (3) T = w R = w sin θ (4) T = w sin θ R = w cot θ

Q13.A spring of force constant 800 N/m has an extension of 5 cm. The work done is extending it from 5 cm to 15 cm is (1) 16 J option 1 goes here (2) 8 J (3) 32 J (4) 24 J

Q14.A ball whose kinetic energy is E, is projected at an angle of 45∘ to the horizontal. The kinetic energy of the ball at the highest point of its flight will be (1) E (2) E/√2 (3) E/2 (4) zero

Q15.Two identical particles move towards each other with velocity 2v and v respectively. The velocity of centre of mass is (1) v (2) v/3 (3) v/2 (4) zero JEE Main 2002 JEE Main Previous Year Paper

Q16.Initial angular velocity of a circular disc of mass M is ω1 . Then two small spheres of mass m are attached gently to diametrically opposite points on the edge of the disc. What is the final angular velocity of the disc? (1) ( M+mM )ω1 (2) ( M+mm )ω1 (3) ( M+4M m )ω1 (4) ( M+2mM )ω1

Q18.Moment of inertia of a circular wire of mass M and radius R about its diameter is (1) MR2/2 (2) MR2 (3) 2MR2 (4) MR2/4

Q19.A particle of mass m moves along line PC with velocity v as shown. What is the angular momentum of the particle about P? (1) mvL (2) mvl (3) mvr (4) zero

Q20.The kinetic energy needed to project a body of mass m from the earth surface (radius R ) to infinity is (1) mgR/2 (2) 2mgR (3) mgR (4) mgR/4

Q22.Energy required to move a body of mass m from an orbit of radius 2R to 3R is (1) GMm/12R2 (2) GMm/3R2 (3) GMm/8R (4) GMm/6R