When a body of mass $m$ just begins to slide as shown, match List-I with List-II:

**List-I**
(a) Normal react

Question

When a body of mass $m$ just begins to slide as shown, match List-I with List-II:

**List-I**
(a) Normal reaction
(b) Frictional force ($f_s$)
(c) Weight ($mg$)
(d) $mg \sin 	heta$

**List-II**
(i) $P$
(ii) $Q$
(iii) $R$
(iv) $S$

Accepted Answer

1. **Analyze the Physical Situation:** A body is on an inclined plane and just begins to slide down. This is a case of limiting friction.
2. **Identify Forces:**
   - **Weight ($mg$):** Acts vertically downwards towards the center of the earth. In standard diagrams, this vector is often labeled pointing straight down (Label $R$).
   - **Normal Reaction ($N$):** Acts perpendicular to the contact surface, directed away from the plane. (Label $S$).
   - **Frictional Force ($f_s$):** Opposes the tendency of motion. Since the body tends to slide down, friction acts up the inclined plane. (Label $Q$).
   - **Component $mg \sin 	heta$:** This is the component of weight acting parallel to the inclined plane, pulling the body down. (Label $P$).
3. **Match with List-II:**
   - (a) Normal reaction $ightarrow$ (iv) $S$ (Perpendicular outward)
   - (b) Frictional force ($f_s$) $ightarrow$ (ii) $Q$ (Up the incline)
   - (c) Weight ($mg$) $ightarrow$ (iii) $R$ (Vertically down)
   - (d) $mg \sin 	heta$ $ightarrow$ (i) $P$ (Down the incline)
4. **Select Option:** The matching sequence is (a)-(iv), (b)-(ii), (c)-(iii), (d)-(i), which corresponds to Option 2.
   (Reference: NCERT Class 11, Physics Part I, Chapter 5: Laws of Motion, Section 5.9 and Figure 5.11/4.11 depict the free-body diagram of a mass on an incline).

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