Glide ratio is maximized when parasite drag equals induced drag.

Glide ratio is maximized when parasite drag equals induced drag.

• A. Parasite drag equals induced drag
• B. Parasitic drag is zero
• C. Induced drag equals weight
• D. Lift equals weight

Answer: (A)

Glide ratio is maximized when the total drag is as small as possible for the lift you must produce to balance the weight. In gliding, lift equals weight, so maximizing lift‑to‑drag (L/D) means minimizing drag. Total drag consists of two parts: parasite drag, which grows with speed (it’s the drag on the airframe itself), and induced drag, which decreases with speed (it’s produced by generating lift). As you speed up, parasite drag rises while induced drag falls, so the two drag terms balance at a specific speed. At that balance point, their sum—the total drag—is minimized, and since L is fixed by weight, the lift-to-drag ratio is at its best, giving the longest glide. That’s why the condition is parasite drag equal to induced drag. The other ideas don’t capture why the drag is minimized at that speed: zero parasite drag is not physically achievable in flight, lift equaling weight is true in steady flight but doesn’t specify the speed for minimum drag, and induced drag equaling weight isn’t the criterion that yields the smallest total drag.

Glide ratio is maximized when the total drag is as small as possible for the lift you must produce to balance the weight. In gliding, lift equals weight, so maximizing lift‑to‑drag (L/D) means minimizing drag.

Total drag consists of two parts: parasite drag, which grows with speed (it’s the drag on the airframe itself), and induced drag, which decreases with speed (it’s produced by generating lift). As you speed up, parasite drag rises while induced drag falls, so the two drag terms balance at a specific speed. At that balance point, their sum—the total drag—is minimized, and since L is fixed by weight, the lift-to-drag ratio is at its best, giving the longest glide.

That’s why the condition is parasite drag equal to induced drag. The other ideas don’t capture why the drag is minimized at that speed: zero parasite drag is not physically achievable in flight, lift equaling weight is true in steady flight but doesn’t specify the speed for minimum drag, and induced drag equaling weight isn’t the criterion that yields the smallest total drag.