题干

“10米折返跑”的成绩反应了人体的灵敏素质.测定时,在平直跑道上,受试者以站立式起跑姿势站在起点终点线前,当听到“跑”的口令后,全力跑向正前方10米处的折返线,测试员同时开始计时,受试者到达折返线处时,用手触摸折返线的物体(如木箱),再转身跑向起点终点线,当胸部到达终点线的竖直面时,测试员停表,所用时间即为“10米折返跑”的成绩.设受试者起跑的加速度为4m/s2,运动过程中的最大速度为4m/s,快到达折返线处时需减速到零,减速的加速度为8m/s2,返回时达到最大速度后不需减速,保持最大速度冲线.求该受试“10米折返跑”的成绩为多少秒?

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答案(点此获取答案解析)

解:对受试者,由起点终点线向折返线运动的过程中
加速阶段据运动学公式得:t1=
v
m
a
1
=1s; s1

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