The most detailed study yet of the physics of a finger snap (响指) has shown that in terms of acceleration (加速度), no other body movement comes close. Using high speed cameras, the researchers found that it reached a speed about 20 times faster than the blink of an eye. This “rotational (旋转的) acceleration” was nearly three times greater than the previous record for humans, set by a professional baseball player's arm.

The research, published in the Journal of the Royal Society Interface, divides the finger snap into three stages. First, force is first built up by pressing the thumb and middle fingers together. This appears to be stored in springlike muscle in the fingers and forearm. Friction (摩擦力) between the two fingers acts like a latch (门闩), preventing the energy from being released. Eventually, an “unlatching” process begins, with the thumb moving sideways and the middle finger quickly sliding past the thumb, starting the snap motion. The middle finger then slips into the palm, generating shockwaves that result in a “pop” sound.

The study was inspired by the Hollywood movie Avengers: Infinity War and the character Thanos, who destroys half the universe by snapping his fingers. He does this while wearing a metal glove. When they saw this scene, Dr Saad Bhamla, the leading researcher, and his colleagues asked themselves if this was possible - could you snap your fingers while wearing a metal glove?

They explored the role of friction by covering fingers with different materials, including metallic thimbles (金属套管), which reduced friction. The researchers concluded that a “Goldilocks zone” of friction was necessary. Too little friction and not enough energy was stored to power the snap. Too much friction led to displacement of energy as the fingers took longer to slide past each other, “wasting” the stored energy as heat. “Our results suggest that Thanos could not have snapped because of his metal armoured fingers. So, it's probably the Hollywood special effects, rather than actual physics, at play,” said Bhamla.

【小题1】What can we learn from paragraph 1?

A．The finger snap is the fastest acceleration of our body.

B．The blink of an eye is faster than a finger snap.

C．People can have faster acceleration if they want.

D．Baseball players have the fastest acceleration.

【小题2】What does the underlined word “This” in paragraph 2 refer to?

A．The position of the thumb.	B．The rotational acceleration.
C．Friction between two fingers.	D．Potential energy from pressing fingers.

【小题3】Why did the researchers conduct the study?

A．They questioned a movie scene.

B．They suspected the function of fingers.

C．They wanted to prove a theory in the movie.

D．They hoped to create different movie scenes.

【小题4】What did the researchers find in the end?

A．A finger snap can happen in any movie.

B．Wearing a metal glove can snap a magic sound.

C．The finger snap of Thanos in the movie is just a play.

D．The friction between fingers is occasionally out of control.