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自然科學 大學

4.59答案為什麼是a

mass, are 「 PASSAGE PROBLEMS 了 R/S BODY. Dancers experience jjmps they make. Tor example Speed7 sma- jZOnta] ) case7? he box )n foT 7 ere no an en- )1S at- 了1S and 1S Ve Up- glvVen 「graph 1 TV planet, when a dancef ]an head by 過e neck cause 負e head to $ 9g.4% of atypical personsm Janding after a Vertical Jump $ 4.0 m/s to restinatime of 0.20 S. 4,57 What 1$ the magnitude Of the average force that her neck exerts on her head during the ]anding? (3) ON; (b) 6O N; (c) 120 N: must exceed the jow down and come to Tes- The head is about as8. Video analysis ot a 65-kg dancer hows that her head decelerates from hthe force her neck exerts on her head during the ]anding, the force her head exerts On her neck 1S (3) the Sames: (b) greater; (co) smaller: (d) greater during the first half ot the land- uring the second halt of the ]anding. 4.,58 Compared Wit 9 and smaller d 4,59 While the dancer 1S in the air and holding a fixed bose what is the magnitude of the force her neck exertS On her heady (3 ON; (b) 6O N; (o]) 120 N; (0) 180 N. 4.60 The forces ona dancer can be measSsured directly When a dancer performs aJump On a force plate that measSures the 10rfce betWween her feet and the ground. A graph Of force verSus time es a Vertical jump performed on aforce plate is Shown lt es at 1S happening at 0.4 $? The dancer is (3) bendlng 0 1S acceleratling downward; (b) pushtung er legs and is almost ready to leave the ground (o in the air and at the to have just touched the 一 her jump; (d) landing and her feel Figure P4.60

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