What is the horizontal component of the initial velocity for the projectile launched at 30 degrees with speed 20 m/s?

• A. About 17 m/s
• B. About 10 m/s
• C. About 20 m/s
• D. About 25 m/s

Answer: (A)

Decompose the initial velocity into horizontal and vertical parts using trigonometry. The horizontal component is v0 cos theta. With v0 = 20 m/s and theta = 30°, v_x = 20 cos 30° = 20 × (√3/2) ≈ 20 × 0.866 ≈ 17.3 m/s, about 17 m/s. This is smaller than the total speed because the motion is angled above the horizontal. (For context, the vertical component is 20 sin 30° = 10 m/s.) Since there’s no horizontal acceleration (ignoring air resistance), the horizontal velocity remains about 17 m/s throughout. Therefore, the best answer is about 17 m/s.