A ball is projected horizontally from the top of a tower. Neglecting air resistance, which of the following…

Analyze the question: A ball is projected horizontally from a tower, and air resistance is ignored. We need to decide which of the three statements are true.

Concept: With no air resistance, the only force on the ball is its weight, W = mg, which acts vertically downward. The horizontal and vertical motions are independent:

• Horizontally, there is no force, so the horizontal velocity is constant.
• Vertically, the ball falls freely with constant acceleration g (about 10 m/s²).

Checking each statement:

I. Vertical acceleration decreases as it falls: FALSE. The vertical acceleration is always g, which is constant near the Earth's surface. It does not decrease.

II. The vertical force on the ball remains constant: TRUE. The vertical force is the weight, mg. Mass and g do not change, so the force is constant.

III. The vertical speed increases as it falls: TRUE. Since the ball accelerates downward at g, the vertical velocity follows v = u + gt. With initial vertical velocity u = 0, v = gt, which grows steadily with time.

Result: Only statements II and III are correct.

**Answer: D (II and III only).

Exam tip: For projectile questions, remember "horizontal: constant velocity, no acceleration; vertical: constant acceleration g, with speed increasing when falling." If a statement says g or the weight changes during a short fall, it is almost certainly false.