A text with many blanks will appear on the screen. You have to choose the correct words from the given box to fill each blank with a correct word.
A mini helicopter modelled on flying tree seeds could soon be flying overhead. Evan Ulrichand colleagues at the University of Maryland in College Park (1) ………..to the biological world for inspiration to build a scaled-down helicopter that could mimic the properties of full-size aircraft. The complex (2) …………of full-size helicopters gets less efficient when shrunk, (3) …………that standard mini helicopters expend most of their power simply fighting to stay stable in the air. The researchers realised that a simpler aircraft designed to stay stable passively would use much less power and reduce manufacturing costs to boot. It turns out that nature (4) ………. them to it. The seeds of trees such as the maple have a single-blade structure that (5) ……….them to fly far away and drift safely to the ground. These seeds, known as samaras, need no engine to spin through the air, thanks to a process called autorotation. By analysing the behaviour of the samara with high-speed cameras, Ulrich and his team were able to copy its design. The samara copter is not the first single-winged helicopter – one was flown in 1952, and others have been attempted since – but it is the first to take advantage of the samara’s autorotation. This allows Ulrich’s vehicle to perform some neat tricks, such as falling safely to the ground if its motor fails or using vertical columns of air to stay aloft indefinitely. “We can turn off the motor and autorotate, which requires no power to sustain,” says Ulrich.
(1) Spin, (2) flourish, (3) beaten, (4) has, (5) meaning, (6) sticks, (7) design, (8) makes, (9) allows, (10) caught