JEE Main 202528 JanuaryMorning Shift
- Exam
- JEE Main
- Year
- 2025
- Date
- 28 January
- Shift
- Morning Shift
- Subject
- Physics
- Chapter
- Center of Mass, Momentum and Collision
JEE Main 2025 · 28 January · Morning Shift · Physics · Center of Mass, Momentum and Collision
The center of mass of a thin rectangular plate (fig - x ) with...
The center of mass of a thin rectangular plate (fig - x ) with sides of length and , whose mass per unit area varies as (where is a constant), would be

Options
- A
- B
- C
- D
Correct answer
A.
Step-by-step solution
\begin{aligned} & d m=\sigma d A \\ & \begin{aligned} d & =\sigma(d x)(d y)=\frac{\sigma_0 x}{a b}(d x)(d y) \\ x_{c o m} & =\frac{\int x d m}{\int d m}=\frac{\int x \frac{\left(\sigma_0 x\right)}{a b}(d x)(d y)}{\int_0 \frac{\sigma_0}{a b}(d x)(d y)} \\ & =\frac{\int_0^a x^2 d x \int_0^b d y}{\int_0^b x d x \int_0^b d y}=\frac{2 a}{3} \\ y_{c o m} & =\frac{\int y d m}{\int d m}=\frac{\int y\left(\frac{\sigma_0 x}{a b}\right)(d x)(d y)}{\int \frac{\sigma_0 x}{a b}(d x)(d y)}\end{aligned}\end{aligned}=\frac{\int_0^a x d x \int_0^b y d y}{\int_0^a x d x \int_0^b d y}=\frac{b}{2}
i.e., \vec{r}_{\mathrm{com}}\equiv \left(\frac{2 a}{3},\frac{b}{2}\right)