New Delhi: “A helicopter is flying horizontally at a constant speed. A perfectly flexible uniform cable is suspended beneath the helicopter. Air friction on the cable is not negligible. Which of the following diagrams best shows the shape of the cable as the helicopter flies through the air to the right?”
Derek Muller, who runs the YouTube channel Veritasium, rented a helicopter recently to find the answer to the question, which was asked in the 2014 US Physics Olympiad.
The question had then generated a lot of controversies as no one agreed on a common answer. People’s interest in solving the question remains to this day.
Muller thought of settling it once and for all.
In the video, he lowers a cable from the chopper to see how it flies to arrive at his answer. Muller funded the ride from sponsorship deals.
Muller explains in his video that there are two external forces acting on the rope: gravity, pulling it downwards, and air resistance, moving it to the left. “When flying along at constant speeds, these forces must be perfectly balanced by the tension in the rope,” he says.
The 2014 exam paper is now posted on the American Association of Physics Teachers’ (AAPT) website. In the solutions section, it explains that “since there is air friction on the cable, then there must be a horizontal component to the force where the cable attaches to the helicopter”.
