In projectile motion, what is true about horizontal acceleration?

• A. It is zero.
• B. It is zero when height changes.
• C. It equals gravity.
• D. It is negative.

Answer: (A)

In projectile motion, horizontal acceleration is zero because there are no horizontal forces acting on the projectile (ignoring air resistance). Gravity pulls straight downward, giving a vertical acceleration of magnitude g, but it does not cause any change in the horizontal speed. As a result, the horizontal component of acceleration remains zero no matter how the height changes. The projectile can rise or fall while its horizontal velocity stays constant, assuming no drag. The other statements don’t fit: gravity acts vertically, not horizontally; height change doesn’t create horizontal acceleration; and stating a horizontal acceleration as negative would imply a direction, but the actual horizontal acceleration is simply zero.