The acceleration of a body sliding down a smooth inclined plane making an angle of 30° with the horizontal is (g = 10 m/s²):

**The reasoning** When a body slides down a *smooth* (frictionless) inclined plane, only one component of gravity pulls it down the slope. We need to **resolve gravity** into two parts: - Component parallel to the plane = g sin θ (this accelerates the body) - Component perpendicular to plane = g cos θ (balanced by normal force) The acceleration down the plane = **g sin θ** With θ = 30° and g = 10 m/s²: a = 10 × sin 30° a = 10 × 0.5 **a = 5 m/s²** **Why the wrong options tempt you** - **A (10 m/s²)** — This is if you forgot the angle matters and used full gravity - **B (8.66 m/s²)** — You used *cos 30°* instead of sin 30° (cos 30° ≈ 0.866). Easy mix-up! - **D (2.5 m/s²)** — Maybe you divided by 4 instead of 2, or confused the setup entirely **Quick takeaway** On a smooth incline, acceleration = **g sin θ** — only the *sine* component pulls the object down the slope, and sin 30° always equals ½.