Physics Circle home Student Login

Home›Chapters›Centre of Mass PYQs›Composite & Cut-Out Bodies›Question 7

JEE Main 2020 (8 Jan, Shift 1) · Composite & Cut-Out Bodies

Composite & Cut-Out Bodies question from JEE Main 2020 (8 Jan, Shift 1)

Q7JEE Main 2020 · 8 JAN · SHIFT 1Medium

Composite & Cut-Out Bodies

The coordinates of centre of mass of a uniform flag shaped lamina (thin flat plate) of mass 4kg. (The coordinates of the same are shown in figure) are:

Figure

Show answer and solution

Answer: (a)

  1. Split the flag into two rectangles of uniform density, so mass ∝\propto area.
  2. Rectangle 1: 0≤x≤1, 0≤y≤30\le x\le 1,\ 0\le y\le 3, area 33, centre (0.5, 1.5)(0.5,\ 1.5).
  3. Rectangle 2: 1≤x≤2, 2≤y≤31\le x\le 2,\ 2\le y\le 3, area 11, centre (1.5, 2.5)(1.5,\ 2.5).
  4. xcm=3(0.5)+1(1.5)4=0.75x_{cm} = \frac{3(0.5)+1(1.5)}{4} = 0.75 m,  ycm=3(1.5)+1(2.5)4=1.75\ y_{cm} = \frac{3(1.5)+1(2.5)}{4} = 1.75 m
  5. So the answer is (a) (0.75 m, 1.75 m)(0.75\text{ m},\ 1.75\text{ m}).
Report a mistake

More questions on Composite & Cut-Out Bodies