JEE Main 2025 Jan 28 Shift 1 — Physics

The center of mass of a thin rectangular plate (fig - x) with sides of length $a$ and $b$, whose mass per unit area ($\sigma$) varies as $\sigma = \frac{\sigma_0 x}{ab}$ (where $\sigma_0$ is a constant), would be _____

fig-x — a rectangular plate in the x-y plane with one corner at origin O, side $a$ along the x-axis and side $b$ along the y-axis

A bead of mass 'm' slides without friction on the wall of a vertical circular hoop of radius 'R' as shown in figure. The bead moves under the combined action of gravity and a massless spring (k) attached to the bottom of the hoop. The equilibrium length of the spring is 'R'. If the bead is released from top of the hoop with (negligible) zero initial speed, velocity of bead, when the length of spring becomes 'R', would be (spring constant is 'k', g is accleration due to gravity)

a vertical circular hoop of diameter 2R resting on the ground, with a spring attached from the bottom of the hoop to the bead at the top

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R

Assertion A: In a central force field, the work done is independent of the path chosen.

Reason R: Every force encountered in mechanics does not have an associated potential energy.

In the light of the above statements, choose the most appropriate answer from the options given below

Consider following statements:

A. Surface tension arises due to extra energy of the molecules at the interior as compared to the molecules at the surface, of a liquid.

B. As the temperature of liquid rises, the coefficient of viscosity increases.

C. As the temperature of gas increases, the coefficient of viscosity increases

D. The onset of turbulence is determined by Reynold's number.

E. In a steady flow two stream lines never intersect.

Choose the correct answer from the options given below:

In the experiment for measurement of viscosity '$\eta$' of given liquid with a ball having radius R, consider following statements.

A. Graph between terminal velocity V and R will be a parabola.

B. The terminal velocities of different diameter balls are constant for a given liquid.

C. Measurement of terminal velocity is dependent on the temperature.

D. This experiment can be utilized to assess the density of a given liquid.

E. If balls are dropped with some initial speed, the value of $\eta$ will change.

For a particular ideal gas which of the following graphs represents the variation of mean squared velocity of the gas molecules with temperature?

A Carnot engine (E) is working between two temperatures 473K and 273K. In a new system two engines - engine $E_1$ works between 473K to 373K and engine $E_2$ works between 373K to 273K. If $\eta_{12}$, $\eta_1$ and $\eta_2$ are the efficiencies of the engines E, $E_1$ and $E_2$, respectively, then

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R

Assertion A: A sound wave has higher speed in solids than gases.

Reason R: Gases have higher value of Bulk modulus than solids.

In the light of the above statements, choose the correct answer from the options given below

A wire of resistance R is bent into an equilateral triangle and an identical wire is bent into a square. The ratio of resistance between the two end points of an edge of the triangle to that of the square is

Consider a long thin conducting wire carrying a uniform current I. A particle having mass "M" and charge "q" is released at a distance "$a$" from the wire with a speed $v_o$ along the direction of current in the wire. The particle gets attracted to the wire due to magnetic force. The particle turns round when it is at distance $x$ from the wire. The value of $x$ is

[$\mu_0$ is the permeability of vacuum]

Find the equivalent resistance between two ends of the following circuit

circuit between two terminals — three resistors each of value $r/3$: two in series along the lower branch, with a plain wire bridging across the first two, and the third resistor ($r/3$) in the right portion, with connecting wire loops above and below

A particle of mass 'm' and charge 'q' is fastened to one end 'A' of a massless string having equilibrium length $l$, whose other end is fixed at point 'O'. The whole system is placed on a frictionless horizontal plane and is initially at rest. If a uniform electric field is switched on along the direction as shown in figure, then the speed of the particle when it crosses the x-axis is

x-y axes with origin at O; a uniform electric field E points along the +x direction; the string OA of length $l$ makes an angle of 60° with the x-axis, with the particle at end A

Two capacitors $C_1$ and $C_2$ are connected in parallel to a battery. The charge-time graph for both the capacitors is shown below. The energies stored in them are $U_1$ and $U_2$ respectively. Which of the given statements is true?

graph of charge q vs time t showing two rising curves — curve $C_1$ rises faster initially and saturates at a lower charge; curve $C_2$ rises slower but saturates at a higher charge

Three infinitely long wires with linear charge density $\lambda$ are placed along the x-axis, y-axis and z-axis respectively. Which of the following denotes an equipotential surface?

Due to presence of an em-wave whose electric component is given by $E = 100 \sin(\omega t - kx)\ \mathrm{NC^{-1}}$, a cylinder of length 200 cm holds certain amount of em-energy inside it. If another cylinder of same length but half diameter than previous one holds same amount of em-energy, the magnitude of the electric field of the corresponding em-wave should be modified as

A hemispherical vessel is completely filled with a liquid of refractive index $\mu$. A small coin is kept at the lowest point (O) of the vessel as shown in figure. The minimum value of the refractive index of the liquid so that a person can see the coin from point E (at the level of the vessel) is _____.

a hemispherical vessel filled with liquid, rim points A and B at the top with centre C; coin at the lowest point O; point E lies outside the vessel at the level of the rim, to the right of B

A thin prism $P_1$ with angle 4° made of glass having refractive index 1.54, is combined with another thin prism $P_2$ made of glass having refractive index 1.72 to get dispersion without deviation. The angle of the prism $P_2$ in degrees is

A proton of mass '$m_p$' has same energy as that of a photon of wavelength '$\lambda$'. If the proton is moving at non-relativistic speed, then ratio of its de Broglie wavelength to the wavelength of photon is.

Choose the correct nuclear process from the below options

[p: proton, n: neutron, $e^-$: electron, $e^+$: positron, $\nu$: neutrino, $\bar{\nu}$: antineutrino]

Which of the following circuits has the same outpur as that of the given circuit?

logic circuit — inputs A and B; B is passed through a NOT gate; one AND gate receives A and NOT B, another AND gate receives A and B; the outputs of the two AND gates feed a NOR gate whose output is Y

In a measurement, it is asked to find modulus of elasticity per unit torque applied on the system. The measured quantity has dimension of $[\mathrm{M^a\, L^b\, T^c}]$. If b = 3, the value of c is _____

A tiny metallic rectangular sheet has length and breadth of 5 mm and 2.5 mm, respectively. Using a specially designed screw gauge which has pitch of 0.75 mm and 15 divisions in the circular scale, you are asked to find the area of the sheet. In this measurement, the maximum fractional error will be $\frac{x}{100}$ where $x$ is ________ .

Two iron solid discs of negligible thickness have radii $R_1$ and $R_2$ and moment of intertia $I_1$ and $I_2$, respectively. For $R_2 = 2R_1$, the ratio of $I_1$ and $I_2$ would be $1/x$, where $x$ = _____.

The moment of inertia of a solid disc rotating along its diameter is 2.5 times higher than the moment of inertia of a ring rotating in similar way. The moment of inertia of a solid sphere which has same radius as the disc and rotating in similar way, is n times higher than the moment of inertia of the given ring. Here, n = _____. Consider all the bodies have equal masses.

A double slit interference experiment performed with a light of wavelength 600 nm forms an interference fringe pattern on a screen with 10th bright fringe having its centre at a distance of 10 mm from the central maximum. Distance of the centre of the same 10th bright fringe from the central maximum when the source of light is replaced by another source of wavelength 660 nm would be _____ mm.