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Physics · Rotational Dynamics

JEE Main 2025 — 4 April, Morning Shift — Question 53

Which of the following are correct expression for torque acting on a body?

A. τ⃗=r⃗×L⃗\vec{\tau}=\vec{r} \times \vec{L}

B. τ⃗=ddt(r⃗×p⃗)\vec{\tau}=\frac{d}{d t}(\vec{r} \times \vec{p})

C. τ⃗=r⃗×dp⃗dt\vec{\tau}=\vec{r} \times \frac{d \vec{p}}{d t}

D. τ⃗=Iα⃗\vec{\tau}=I \vec{\alpha} E. τ⃗=r⃗×F⃗\vec{\tau}=\vec{r} \times \vec{F} ( r⃗=\vec{r}= position vector; p⃗=\vec{p}= linear momentum; L⃗=\vec{L}= angular momentum; α⃗=\vec{\alpha}= angular acceleration; I=I= moment of inertia; F⃗=\vec{F}= force; t=t= time) Choose the correct answer from the options given below:

  1. Option A:

    B, D and E Only

  2. Option B:

    A, B, D and E Only

  3. Option C:

    B, C, D and E Only

    Correct
  4. Option D:

    C and D Only

Answer: C

Step-by-step solution

τ⃗=r⃗×L⃗\vec{\tau}=\vec{r} \times \vec{L} wrong τ⃗=ddt(r⃗×p⃗)\vec{\tau}=\frac{d}{d t}(\vec{r} \times \vec{p})

correct τ⃗=r⃗×dp⃗dt=r⃗×F⃗\vec{\tau}=\vec{r} \times \frac{d \vec{p}}{d t}=\vec{r} \times \vec{F}

correct τ⃗=∥α⃗\vec{\tau}=\| \vec{\alpha} \quad correct τ⃗=r⃗×F⃗\vec{\tau}=\vec{r} \times \vec{F} \quad correct

Answer key and solution verified before publishing.

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Exam
JEE Main 2025
Paper
4 April, Morning Shift
Subject
Physics
Chapter
Rotational Dynamics
Topic
Torque, Equation of Motion and Toppling

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