Practice Questions

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

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

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 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 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 .

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

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.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.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

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 ]

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.

Q26.The amplitude of wave disturbance propagating in the positive x-direction is given by y = 1 at time t = 0 (1+x)2 and y = 1 at t = 1 s, where x and y are in metres. The shape of wave does not change during the 1+(x−2)2 propagation. The velocity of the wave will be m s−1.

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

Q26.The electric field in a region is given by E = 5 E0ˆi + 5 E0ˆj field through a rectangular surface, area 0. 4 m2 parallel to the Y −Z plane is _______ N m2 C−1 .

Q26.A uniform heating wire of resistance 36 Ω is connected across a potential difference of 240 V . The wire is then cut into half and a potential difference of 240 V is applied across each half separately. The ratio of power dissipation in first case to the total power dissipation in the second case would be 1: 𝑥, where 𝑥 is -1

Q26.For an ideal heat engine, the temperature of the source is 127°C. In order to have 60% efficiency the temperature of the sink should be __________ ∘C. (Round off to the nearest integer)

Q27.In Bohr's atomic model, the electron is assumed to revolve in a circular orbit of radius 0. 5 A. If the speed of electron is 2. 2 × 106 m s−1. Then the current associated with the electron will be__________ ×10−2 mA. [Take π as 22 7 ]

Q27.A fringe width of 6 mm was produced for two slits separated by 1 mm apart. The screen is placed 10 m away. The wavelength of light used is x nm. The value of x to the nearest integer is ______.

Q28.A radioactive substance decays to ( 161 )th of its initial activity in 80 days. The half life of the radioactive substance expressed in days is ________.

Q28.A series LCR circuit is designed to resonate at an angular frequency ω0 = 105 rad s−1. The circuit draws 16 W power from 120 V source at resonance. The value of resistance R in the circuit is ________ Ω.

Q28.Two identical conducting spheres with negligible volume have 2. 1 nC and −0. 1 nC charges, respectively. They are brought into contact and then separated by a distance of 0. 5 m. The electrostatic force acting between the spheres is ___ ×10−9 N . [Given : 4πε0 = 9×1091 SI unit]

Q28.A plane electromagnetic wave with a frequency of 30 MHz travels in free space. At a particular point in space and time, the electric field is 6 V m−1 . The magnetic field at this point will be x × 10−8 T. The value of x is,

Q28.The alternating current is given by, i = {√42 sin( 2πT t) 10} __________ A.