Jawaban:

1.

m₁ = 2 kg

x₁ = 0

y₁ = 0

m₂ = 6 kg

x₂ = 4

y₂ = 0

m₃ = 4

x₃ = -2

y₃ = 0

pusat massa X

x = (m₁x₁ + m₂x₂ + m₃x₃ ) / ( m₁ + m₂ + m₃)

x = (2x0 + 6x4 + 4x(-2)) / (2+6+4)

x = 16/12 = 1,33

pusat massa Y

y = (m₁y₁ + m₂y₂ + m₃y₃ ) / ( m₁ + m₂ + m₃)

y = (0+0+0) / 12

y = 0

2.

l = 10 m

d = 3cm, r = 1,5 cm = 0,015m

F = 1500 N

Δl = 0,02 mm = 0,0002 m

a. Tegangan tali σ

σ = F / A

A = πr² =3,14x0,015² = 0,0007065

σ = F / A = 1500 / 0,0007065 = 2123142,2 = 2,12x10⁶ Pa

b. Regangan tali e

e = Δl / l =  0,0002 / 10 = 0,00002 = 2,12x10⁻⁵

c. Modulus young E

E = σ / e = 2123142,2 / 0,00002 = 2,12x10⁶ / 2x10⁻⁵ = 1,06x10¹¹ Pa

Penjelasan: