Practice Questions

Q69.According to EInstein's photoelectric equation, the plot of the kinetic energy of the emitted photo electrons from a metal Vs the frequency, of the incident radiation gives straight line whose slope JEE Main 2004 JEE Main Previous Year Paper (1) depends on the nature of the metal used (2) depends on the intensity of the radiation (3) depends both on the intensity of the radiation and (4) is the same for all metals and independent of the the metal used intensity of the radiation.

Q70.The work function of a substance is 4.0eV . Then longest wavelength of light that can cause photoelectron emission from this substance approximately (1) 540 nm (2) 400 nm (3) 310 nm (4) 220 nm

Q72.A nucleus disintegrates into two nuclear parts which have their velocities in the ratio 2 : 1. The ratio of their nuclear sizes will be (1) 21/3 : 1 (2) 1 : 31/2 (3) 31/2 : 1 (4) 1 : 21/3

Q73.The binding energy per nucleon of deuteron (21H) and helium nucleus (42He) is 1.1MeV and 7MeV respectively. If two deuteron nuclei react to form a single helium nucleus, then the energy released is (1) 13.9MeV (2) 26.9MeV (3) 23.6MeV (4) 19.2MeV

Q74.When npn transistor is used as amplifier (1) electrons move from base to collector (2) holes move from emitter to base (3) electrons move from collector to base (4) holes move from base to emitter.

Q75.For a transistor amplifier in common emitter configuration having load impedance of 1kΩ (hfe = 50 and hoe = 25 ) the current gain is (1) −5.2 (2) −15.7 (3) −24.8 (4) −48.78

Q84.Consider the following nuclear reactions 238 92 M →xyN + 42He N y N →ABL + 2β+ The number of neutrons in the element L is (1) 142 (2) 146 (3) 140 (4) 144

Q1. The length of a simple pendulum executing simple harmonic motion is increased by 21%. The percentage increase in the time period of the pendulum of increased length is (1) 11% (2) 21% (3) 42% (4) 10%

Q2. Dimension of 1 , where symbols have their usual meaning, are μ0ε0 (1) [L−1 T] (2) [L−2 T2] (3) [L2 T−2] (4) [LT−1]

Q3. The physical quantities not having same dimensions are (1) torque and work (2) momentum and Planck's constant (3) stress and Young's modulus (4) speed and (μ0ε0)−1/2

Q4. A car, moving with a speed of 50 km/hr, can be stopped by brakes after at least 6 m. If the same car is moving at a speed of 100 km/hr, the minimum stopping distance is (1) 12 m (2) 18 m (3) 24 m (4) 6 m

Q5. The co-ordinates of a moving particle at any time ' t ' are given by x = αt3 and y = βt3 . The speed of the particle at time ' t ' is given by (1) 3t√α2 + β2 (2) 3t2√α2 + β2 (3) t2√α2 + β2 (4) √α2 + β2

Q6. A body travels a distance s in t seconds. It starts from rest and ends at rest. In the first part of the journey, it moves with constant acceleration f and in the second part with constant retardation r. The value of t is given by (2) 2s ( f1 + 1r ) f 1 + 1r ) (1) √2s ( (3) 1 2 s 1 (4) √2s(f + r) f + r

Q7. Two particles start simultaneously from the same point and move along two straight lines, one with uniform → velocity →u and the other from rest with uniform acceleration f . Let α be the angle between their directions of motion. The relative velocity of the second particle w.r.t. the first is least after a time. (1) u cos α (2) u sin α f f (3) f cos α (4) u sin α. u

Q8. A boy playing on the roof of a 10 m high building throws a ball with a speed of 10 m/s at an angle of 30∘ with the horizontal. How far from the throwing point will the ball be at the height of 10 m from the ground? 1 √3 = 10 m/s2, sin 30∘= , cos 30∘= 2 2 [g ] (1) 5.20 m (2) 4.33 m (3) 2.60 m (4) 8.66 m JEE Main 2003 JEE Main Previous Year Paper

Q9. Two stones are projected from the top of a cliff h metres high, with the same speed u, so as to hit the ground at the same spot. If one of the stones is projected at an angle θ to the horizontal then the θ equals (1) u√2gh (2) √2ugh (3) 2 g√uh (4) 2 h√ug

Q10.A spring balance is attached to the ceiling of a lift. A man hangs his bag on the spring and the spring reads 49 N , when the lift is stationary. If the lift moves downward with an acceleration of 5 m/s2 , the reading of the spring balance will be (1) 24 N (2) 74 N (3) 15 N (4) 49 N

Q11.Three forces start acting simultaneously on a particle moving with velocity, →v. These forces are represented in magnitude and direction by the three sides of a triangle ABC. The particle will now move with velocity (1) less than →v (2) greater than →v (3) |v| in the direction of the largest force BC (4) →v, remaining unchanged

Q12.A horizontal force of 10 N is necessary to just hold a block stationary against a wall. The co-efficient of friction between the block and the wall is 0.2 . The weight of the block is (1) 20 N (2) 50 N (3) 100 N (4) 2 N

Q13.A marble block of mass 2 kg lying on ice when given a velocity of 6 m/s is stopped by friction in 10 s. Then the coefficient of friction is (1) 0.02 (2) 0.03 (3) 0.04 (4) None of these

Q14.A block of mass M is pulled along a horizontal frictionless surface by a rope of mass m. If a force P is applied at the free end of the rope, the force exerted by the rope on the block is (1) Pm (2) Pm M+m M−m (3) P (4) PM M+m JEE Main 2003 JEE Main Previous Year Paper

Q16.A rocket with a lift-off mass 3.5 × 104 kg is blasted upwards with an initial acceleration of 10 m/s2 . Then the initial thrust of the blast is (1) 3.5 × 105 N (2) 7.0 × 105 N (3) 14.0 × 105 N (4) 1.75 × 105 N

Q18.A spring of spring constant 5 × 103 N/m is stretched initially by 5 cm from the unstretched position. Then the work required to stretch it further by another 5 cm is (1) 12.50 N −m (2) 18.75 N −m (3) 25.00 N −m (4) 6.25 N −m

Q19.A body is moved along a straight line by a machine delivering a constant power. The distance moved by the body in time ' t ' is proportional to (1) t3/4 (2) t3/2 (3) t1/4 (4) t1/2

Q20.A circular disc X of radius R is made from an iron plate of thickness t, and another disc Y of radius 4R is made from an iron plate of thickness t . Then the relation between the moment of inertia IX and IY is 4 (1) IY = 32Ix (2) IY = 16Ix (3) IY = IX (4) IY = 64IX