Respostas

2013-10-03T17:57:02-03:00
Letra A)

S = So + vot + at²/2

20 = 0 + 0t + a*4² / 2

20 = 8 a

20/8 = a

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a = 2,5m/s²
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Fr = m * a

Fr = 5 * 2,5

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Fr = 12,5N (Força resultante)
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Letra B) 

S = So + Vot + at²/2
S = 0 + 0t + 2,5 * 30² / 2

S = 2,5 * 900 / 2

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S = 1125 metros // Distancia percorrida
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ei responde oltra atividade pra min