physics - force

2010-04-18 4:53 am

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problem 4.37果題..佢究竟想問乜ｇａ...? 咩weight...?
ah...>< 唔該話我知點做至岩丫~* thx^^

更新1:

補充* Part A: Find the magnitude of the smallest force that the child should exert. You can ignore the effects of friction. F=16.6N Part B:Find the angle that the force makes with the +x-direction. Take angles measured counterclockwise from the +x-direction to be positive. theta=270 Part C: W=840N why!?

回答 (2)

[匿名]

2010-04-18 7:45 pm

✔ 最佳答案

Part C:

net force acting on the cart=140cos30+100cos60
F=ma
m=(140cos30+100cos60)/2=85.6kg
Weight=mg=85.6*10=856N

Part C:
W=840N
why!?
可能係佢用g=9.80665ms^-2後取3sig.fig,之後有誤差吧...
Weight=mg=85.6*9.80665=839.66N=840N(corr 3sig.fig,)

Quote from wiki: Standard gravity, usually denoted by g0 or gn, is the nominal acceleration due to gravity at the Earth's surface at sea level, defined to be precisely 9.80665 m/s2 (~32.174 ft/s2). This value was established by the 3rd CGPM (1901, CR 70).

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天同

2010-04-18 8:05 am

1. What are part (A) and part (B)? In what direction did the child exert a foce on the cart?

2. Use: force = mass x acceleration
hence, F = (6+4) x 2.8 N = 28 N

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