A projectile is launched horizontally from a height of 45 m with initial horizontal velocity 20 m/s. Neglect air resistance. Approximately how far does it travel horizontally before hitting the ground?

• A. 100 m
• B. 60 m
• C. Approximately 60.6 m
• D. 45 m

Answer: (C)

When air resistance is neglected, horizontal motion is independent of vertical motion. The horizontal speed stays constant at 20 m/s, while the time to hit the ground is determined only by the vertical drop from 45 m.

For vertical motion, starting from rest in the vertical direction, the drop distance is h = (1/2) g t^2. Solve for t: t = sqrt(2h/g) = sqrt(2×45 / 9.8) ≈ sqrt(90 / 9.8) ≈ sqrt(9.18) ≈ 3.03 s.

During that time, the object travels horizontally: distance = v_x × t = 20 m/s × 3.03 s ≈ 60.6 m.

So the horizontal distance before hitting the ground is about 60.6 meters.