超難力學問題

Let F = Net force act on the balloon after the string broken
F = ma,
= (50÷1000)(2)
= 0.1N

The ball is at rest before the string is broken.
i.e. The upward force – the downward force = 0
F – T = 0
F = T
T = 0.1N

∴The answer is B. 0.1N.

2007-04-02 18:47:08 補充：
thx呀...估唔到你會揀我呀~

before break: T+mg=F (F bouyant force)
after: F-mg=ma=0.05x2=0.1
so T=0.1N

answer係咪d阿..
因為佢向上飛,acceleration係2ms^(-2),但係個gravitaional acceleration向下係10ms^(-2),咁即係o個舊野ge total acceleration係12ms^(-2),所以個波ge total force係0.6ms^(-2)(f=ma)
因為newton's third law,action=reaction,所以個tension係0.6..對嗎?