NEET
- Exam
- NEET
- Subject
- Physics
- Chapter
- Center of Mass, Momentum and Collision
NEET · Physics · Center of Mass, Momentum and Collision
Statement-I: When you lean behind over the hind legs of the chair,...
Statement-I: When you lean behind over the hind legs of the chair, the chair falls back after a certain angle.
Statement-II: Centre of mass lying outside the system makes the system unstable.
Options
- ABoth Statement-I and Statement-II are correct.
- BBoth Statement-I and Statement-II are incorrect.
- CStatement-I is correct and Statement-II is incorrect.
- DStatement-I is incorrect and Statement-II is correct.
Correct answer
A. Both Statement-I and Statement-II are correct.
Step-by-step solution
- Stability criterion: an object is stable as long as the vertical line through its centre of mass (CM) falls inside the base of support. If the vertical from the CM passes outside the base, the normal reaction can no longer provide a balancing moment and the object will tip.
- Apply to the chair. when you lean back on the hind legs you tilt the chair so the projection of the combined CM (you + chair) moves toward the back edge of the base. At a certain tilt angle the vertical through the CM crosses the rear edge - beyond that the CM lies outside the support polygon and the chair rotates (falls) backward. That is exactly Statement-I and it follows from Statement-II.
So both statements are true and related: the chair falls when the CM's vertical leaves the base of support.