Question

Alguém me ajuda na 7 , 8, 9 e 10

Answer 1

7 - a)
$V = V_0 + at \\ V = 0 + 1 \times 20 = 20 \ m/s$
b)
$E_{cinetica} = \frac{mv^2}{2} = \frac{80 \times 20^2}{2} = 16 \ kJ$

8)
72 km/h  = 20 m/s
g = 10 m/s²
$E_{mecanica} = E_{cinetica} + E_{potencial} \\ E_{mecanica} = \frac{mv^2}{2} + mgH \\ E_{mecanica} = \frac{1200 \times 20 ^2}{2} + 1200 \times 10 \times 10 \\ E_{mecanica} = 240000 + 120000 = 360 \ kJ$

9) Conservação de energia:
$E_{inicial} = E_{final} \\ mgH = \frac{mv^2}{2} + Perdas \\ Perdas = mgH - \frac{mv^2}{2} \\ Perdas = 20 \times 10 \times 2 - \frac{20 \times 4^2}{2} \\ Perdas = 400 - 160 = 240 \ J$

10)
$E_{inicial} = E_{final} \\ mgH_A = mgH_B + Perdas \\ Perdas = mgH_A - mgH_B} \\ Perdas = 20 \times 10 \times 1,2 - 20 \times 10 \times 0,8 \\ Perdas = 240 - 160 = 80 \ J$