Acceleration on a frictionless incline

Steps:

• Resolve gravitational force: component parallel to slope is mg sinθ, where θ=30°.
• No friction, so net force down slope is mg sinθ.
• By Newton's second law, acceleration a = (mg sinθ)/m = g sinθ.
• With g=9.8 m/s² and sin30°=0.5, a=9.8 × 0.5 = 4.9 m/s².

Why A is correct:

• Matches formula a = g sinθ for frictionless incline, yielding 4.9 m/s² exactly.

Why the others are wrong:

• B: Incorrect; 5.7 m/s² overestimates sin30° component.
• C: Incorrect; 8.5 m/s² approximates g sin60°, wrong angle.
• D: Incorrect; 9.8 m/s² is full g, ignores incline resolution.

Final answer: A