Respostas

2014-07-23T17:19:43-03:00
7= \frac{a}{2} *4^2

7= \frac{a}{2} *16


7*2=a*16


14=a*16


a= \frac{14}{16}: \frac{2}{2} = \frac{7}{8}m/s^2


De 0s a 2s, a velocidade final é:

V=0+ \frac{7}{8}*2


V= \frac{14}{8} :\frac{2}{2}= \frac{7}{4}m/s


De 2s a 4s, a velocidade final é:

V= \frac{7}{4}+ \frac{7}{8}*2


V= \frac{7}{4}+ \frac{14}{8}: \frac{2}{2} = \frac{7}{4}+ \frac{7}{4}=  \frac{14}{4}= \frac{7}{2} m/s


Para calcularmos a velocidade média entre 2 e 4, basta usarmos a média aritmética:

Vm= \frac{V+Vo}{2}


Vm= \frac{ \frac{7}{2} +\frac{7}{4}  }{2}

Tirando o MMC(2,4)=4


Vm= \frac{ \frac{14+7}{4} }{2}


Vm= \frac{ \frac{21}{4} }{2}


Vm =\frac{21}{4} * \frac{1}{2} = \frac{21}{8} m/s Ou Vm=2,625m/s





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