$\begin{aligned}
& \theta=5 \mathrm{t}^2-8 \mathrm{t} \
& \omega=\frac{\mathrm{d} \theta}{\mathrm{dt}}=10 \mathrm{t}-8 \
& \alpha=\frac{\mathrm{d} \omega}{\mathrm{dt}}=10 \
& \therefore \mathrm{p}=\tau \omega \
& =(\mathrm{I} \alpha) \omega \
& =\left(\frac{\mathrm{mR}^2}{2}\right) \alpha \omega \
& =\left(\frac{\mathrm{mR}^2}{2}\right)(10)(10
\end{aligned}Put\mathrm{t}=2\mathrm{p}=60 \mathrm{mR}^2$
A circular disk of radius R meter and mass M kg is rotating around the axis perpendicular to the disk. An external torque is applied to the disk such…
JEE Main 2025 — Physics Mechanics
2025mcqhard
A circular disk of radius R meter and mass M kg is rotating around the axis perpendicular to the disk. An external torque is applied to the disk such that θ(t)=5t2−8t, where θ(t) is the angular position of the rotating disc as a function of time t. How much power is delivered by the applied torque, when t=2 s ?
Official previous-year question
Held on 23 Jan 2025 · Verified 6 Jul 2026.
Options
- A
72MR2
- B
8MR2
- C
108MR2
- D
60MR2
Did you get this right?
Sign in to track your attempts and accuracy.
Your note
Sign in to keep a private note on this question. Nothing you write is ever public.
JEE Main Mechanics in other years
More JEE Main Mechanics questions
If $\epsilon, E$ and $t$ represent the free space permittivity, electric field and time respectively, then the unit of $\frac{\epsilon E}{t}$ will be :
2026easy
When a part of a straight capillary tube is placed vertically in a liquid, the liquid raises upto certain height $h$. If the inner radius of the capillary tube, density of the liquid and surface tension of the liquid decrease by $1 \%$ each, then the height of the liquid in the tube will change by $\%$.
2026medium
The velocity of a particle is given as $\vec{v} = -x\hat{i} + 2y\hat{j} - z\hat{k}$ m/s. The magnitude of acceleration at point $(1, 2, 4)$ is _______ m/s$^2$.
2026hard
Suppose there is a uniform circular disc of mass $M \mathrm{~kg}$ and radius $r \mathrm{~m}$ shown in figure. The shaded regions are cut out from the disc. The moment of inertia of the remainder about the axis $A$ of the disc is given by $\frac{x}{256} M r^{2}$. The value of $x$ is $\_\_\_\_$. 
2026hard
A soap bubble of surface tension $0.04 \mathrm{~N} / \mathrm{m}$ is blown to a diameter of 7 cm. If $(15000-x) \mu \mathrm{J}$ of work is done in blowing it further to make its diameter 14 cm, then the value of $x$ is $\_\_\_\_$. ($\pi=22 / 7$)
2026medium
Other Physics topics for JEE Main
Keep practicing Mechanics
Work through every JEE Main Mechanics PYQ, year by year.