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標題:
physics about force
發問:
A car moving at speed 50 applied a braking force F and the car stops in 20m. Find F. Given mass of car is 1500kg.
最佳解答:
v^2-u^2 = 2as 0-50^2=2(a)(20) a=-62.5ms-2 F=ma F=1500 x -62.5 F=-93750N(-ve value means the force is towards the backwards direction )
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其他解答:
KE=1/2 mv^2 KE=(1/2)1500(50)^2(1/2) KE=1875000J work done=F//s 187000=F(20) F=937500N|||||50 是甚麼單位... m/s 嗎? 我假設是了哦~~~ v^2 - u^2 = 2as 0^2 - (50)^2 = 2a(20) -2500 = 40a a = -62.5 ms^-2 Therefore, the deceleration of the car is 62.5 ms^-2 . F= ma = (1500)(-62.5) = 93750 N So, the braking force of the car is 93750 F.
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