1
JEE Main 2025 (Online) 28th January Morning Shift
MCQ (Single Correct Answer)
+4
-1
Change Language

Choose the correct nuclear process from the below options [ p : proton, n : neutron, $\mathrm{e}^{-}$: electron, $\mathrm{e}^{+}$: positron, $v:$ neutrino, $\bar{v}:$ antineutrino]

A
$n \rightarrow p+e^{+}+{v}$
B
$\mathrm{n} \rightarrow \mathrm{p}+\mathrm{e}^{-}+\bar{v}$
C
$\mathrm{n} \rightarrow \mathrm{p}+\mathrm{e}^{+}+\bar{v}$
D
$\mathrm{n} \rightarrow \mathrm{p}+\mathrm{e}^{-}+v$
2
JEE Main 2025 (Online) 28th January Morning Shift
MCQ (Single Correct Answer)
+4
-1
Change Language

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

A
$\eta_{12}=\eta_1 \eta_2$
B
$\eta_{12}=\eta_1+\eta_2$
C
$\eta_{12} \geq \eta_1+\eta_2$
D
$\eta_{12}<\eta_1+\eta_2$
3
JEE Main 2025 (Online) 28th January Morning Shift
Numerical
+4
-1
Change Language

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 $R_2=2 R_1$, the ratio of $I_1$ and $I_2$ would be $1 / x$, where $\mathrm{x}=$ _______ .

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4
JEE Main 2025 (Online) 28th January Morning Shift
Numerical
+4
-1
Change Language

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

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