Practice Questions

Q21.If P × Q = Q × P , the angle between P and Q is θ(0°< θ < 360°). The value of θ will be ___ ° .

Q21.The resistance R = VI , where V = (50 ± 2) V and I = (20 ± 0. 2) A . The percentage error in R is x % . The value of x to the nearest integer is ________.

Q21.If the velocity of a body related to displacement x is given by v = √5000 + 24x m s−1, then the acceleration of the body is _________ m s−2.

Q21.Two solids A and B of mass 1 kg and 2 kg respectively are moving with equal linear momentum. The ratio of their kinetic energies (K. E. )A : (K. E. )B will be A1 , so the value of A will be _________.

Q21.The coefficient of static friction between a wooden block of mass 0 . 5 kg and a vertical rough wall is 0 . 2 . The magnitude of the horizontal force that should be applied on the block to keep it adhere to the wall will be______N. 𝑔= 10 m s-2

Q22.A bullet of mass 0. 1 kg is fired on a wooden block to pierce through it, but it stops after moving a distance of 50 cm into it. If the velocity of the bullet before hitting the wood is 10 m s−1 and, it slows down with uniform deceleration, then the magnitude of effective retarding force on the bullet is x N. The value of x to the nearest integer is,

Q22.Two particles having masses 4 g and 16 g respectively are moving with equal kinetic energies. The ratio of the magnitudes of their linear momentum is n : 2 . The value of n will be ___.

Q22.Two persons A and B perform same amount of work in moving a body through a certain distance d with application of forces acting at angles 45° and 60° with the direction of displacement respectively. The ratio of force applied by person A to the force applied by person B is 1 . The value of x is _________. √x

Q22.A person standing on a spring balance inside a stationary lift measures 60 kg . The weight of that person if the lift descends with uniform downward acceleration of 1. 8 m s−2 will be N. [g = 10 m s−2]

Q22.The angular speed of truck wheel is increased from 900 rpm to 2460 rpm in 26 seconds. The number of revolutions by the truck engine during this time is ______. (Assuming the acceleration to be uniform).

Q22.A solid disc of radius 20 cm and mass 10 kg is rotating with an angular velocity of 600 rpm, about an axis normal to its circular plane and passing through its centre of mass. The retarding torque required to bring the disc at rest in 10 s is _________ π × 10−1 N m

Q23.A body rotating with an angular speed of 600 rpm is uniformly accelerated to 1800 rpm in 10 sec. The number of rotations made in the process is

Q23.As shown in the figure, a particle of mass 10 kg is placed at a point A. When the particle is slightly displaced to its right, it starts moving and reaches the point B. The speed of the particle at B is x m s−1 . (Take g = 10 m s−2) The value of x to the nearest integer is

Q24.A pendulum bob has a speed of 3 m s-1 at its lowest position. The pendulum is 50 cm long. The speed of bob, when the length makes an angle of 60° to the vertical will be 𝑔= 10 m s-2 ______ m s-1. JEE Main 2021 (25 Jul Shift 1) JEE Main Previous Year Paper

Q24.A particle executes S.H.M. with amplitude A and time period T . The displacement of the particle when its speed is half of maximum speed is √xA 2 . The value of x is

Q24.The root-mean-square speed of molecules of a given mass of a gas at 27 °C and 1 atmosphere pressure is 200 m s−1. The root-mean-square speed of molecules of the gas at 127 °C and 2 atmosphere pressure is x m s−1. The value of x will be __________. √3

Q24.A resistor dissipates 192 J of energy in 1 s when a current of 4 A is passed through it. Now, when the current is doubled, the amount of thermal energy dissipated in 5 s is _____________ J .

Q25.Two travelling waves produces a standing wave represented by equation. y = (1. 0 mm) cos[(1. 57 cm−1)x] sin[(78. 5 s−1) t]. The node closest to the origin in the region x > 0 will be at x =. . . . . . (in cm).

Q25.A tuning fork is vibrating at 250 Hz. The length of the shortest closed organ pipe that will resonate with the tuning fork will be _____ cm. (Take speed of sound in air as 340 m s−1 )

Q25.A galaxy is moving away from the earth at a speed of 286 km s−1 . The shift in the wavelength of a red line at 630 nm is x × 10−10 m. The value of x, to the nearest integer, is ___ . [Take the value of the speed of the light c, as 3 × 108 m s−1 ]

Q25.The percentage increase in the speed of transverse waves produced in a stretched string if the tension is increased by 4% , will be ___ % .

Q25.A common transistor radio set requires 12 V D . C . for its operation. The D . C . source is constructed by using a transformer and a rectifier circuit, which are operated at 220 V A . C . on standard domestic A . C . supply. The number of turns of secondary coil are 24, then the number of turns of primary are

Q26.At very high frequencies, the effective impedance of the given circuit will be _________Ω .

Q26.In an electrical circuit, a battery is connected to pass 20 C of charge through it in a certain given time. The potential difference between two plates of the battery is maintained at 15 V . The workdone by the battery is _______ J

Q26.A series LCR circuit of R = 5 Ω, L = 20 mH and C = 0. 5 μF is connected across an AC supply of 250 V , having variable frequency. The power dissipated at resonance condition is ________ ×102 W.