Current location - Education and Training Encyclopedia - Resume - Figure A shows the archery scene of China's famous archer Cheng Ming during the 20 14 Incheon Asian Games. It is known that the top span of the bow is L, and the string is even and elastic.
Figure A shows the archery scene of China's famous archer Cheng Ming during the 20 14 Incheon Asian Games. It is known that the top span of the bow is L, and the string is even and elastic.
The moment the bow shoots an arrow, the force is as shown in the figure.

Let the elastic force of the chord at the arrow release point be F 1 and F2, respectively, and the resultant force be f, then F 1=F2=k(2l-l)=kl, and F=2F 1? cosθ，

From the geometric relationship: cosθ=32,

Therefore, the maximum elastic force of the arrow at the moment of launch: F=3kl,

Therefore, choose: d.

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