Mechanics">
2do Examen Fisica I 2023 Solucion
2do Examen Fisica I 2023 Solucion
2do Examen Fisica I 2023 Solucion
1 (3,1)
β
ℓ3 -2 -1 0 1 2 3
⃗F2 X ⃗F2 ℓ2
⃗F3 -1
⃗F1
θ -2 α
(-2,-2) (3,-2)
-3
ℓ1
1
𝑡𝑎𝑛𝛽 = = 0.5 β = 26.56°
2
1
𝑡𝑎𝑛𝜃 = = 1 θ = 45°
1
⃗Ry ⃗Ry
⃗Ry
𝜓 X
⃗Rx
𝑅𝑦 960.42
𝑡𝑎𝑛 𝜓 = = = 1.3286
𝑅𝑥 722.88
𝜓 = 53.032°
b) τ⃗ = (xFy - yFx) 𝑘⃗
3 = xFy3 - yFx3
−2262.72 = x (565.68) - y(−565.68)
-4 = x + y ecuación de la línea ℓ3
Y ⃗F4
⃗
u
ℓ
⃗F1 2ℓ ⃗
-u
ℓ
(-12,3) 37° ⃗F3
⃗2
F
X
x1 x2 x3 x4
12
cos 37 =
3ℓ
4
ℓ= =5
𝑐𝑜𝑠37
𝑥1 = −12 𝑦1 =3
𝑥 = −2ℓ𝑐𝑜𝑠37 = −8 𝑦 = 3 + ℓ𝑠𝑒𝑛37 = 6
{ 2 { 2
𝑥3 =0 𝑦3 = 3 + 3ℓ𝑠𝑒𝑛37 = 12
𝑥4 = ℓ𝑐𝑜𝑠37 = 4 𝑦4 = 3 + 4ℓ𝑠𝑒𝑛37 = 15
𝑥𝑐 = −3
∑ 𝐹𝑖 𝑦𝑖 𝐹1𝑦1 + 𝐹2 𝑦2 + 𝐹3 𝑦3 + 𝐹4𝑦4
𝑦𝑐 = =
𝐹𝑅 𝐹𝑅
𝑦𝑐 = 9.75
O
φ
2ℓ
b2
γ + φ =80
γ = 80 - φ φ
γ
4ℓ
F2 =2ω
b1
a1
a0
F1 =4ω
b2 = ℓcosφ
b1 = a1 – a0 = 2ℓcosγ - 2ℓcosφ
𝑎) ∑ 𝜏𝑂 = 0
𝜏1 + 𝜏2 = 0
𝑏1 𝐹1 − 𝑏2 𝐹2 = 0
𝑏1 𝐹1 = 𝑏2 𝐹2
𝑏1 (4𝜔) = 𝑏2 (2𝜔)
2𝑏1 = 𝑏2
2(2ℓcosγ − 2ℓcosφ) = ℓcosφ
4cosγ − 4cosφ = cosφ
4cosγ = 5cosφ
cosγ = 1.25cosφ
cos(80 – φ) = 1.25cosφ
cos80cosφ + sen80senφ = 1.25cosφ
0.17cosφ + 0.98senφ = 1.25cosφ
0.98senφ = 1.08cosφ
tanφ = 1.102041
φ = 47.78°
𝑅𝐴
A 𝑅𝐵
37° B 𝑅𝐶
ℓ
C
65
E 25°
ℓ 25
100 = ω 53°
62 .65
D
ωʹ = 150
𝑅𝐶
𝑏𝜔ʼ = ℓcos62
┼ E
E
𝑏𝑅𝐵 ▬
(ℓ𝑠𝑒𝑛53)𝑅𝐶 = (ℓ𝑐𝑜𝑠67)𝜔ʼ
𝑐𝑜𝑠62
𝑅𝐶 = (150)
𝑠𝑒𝑛53
𝑅𝐶 = 88.18𝑘𝑔𝑓
𝑅𝐵 𝑏𝜔 = ℓcos62
D
▬ ┼
ℓsen53 = 𝑏𝑅𝐴
D ω = 120
(ℓ𝑠𝑒𝑛53)𝑅𝐵 = (ℓ𝑐𝑜𝑠67)𝜔
𝑐𝑜𝑠62
𝑅𝐵 = (100)
𝑠𝑒𝑛53
𝑅𝐵 = 58.78𝑘𝑔𝑓
c) Equilibrio de traslación: ∑𝐹 = 0
F
x 0 - RAx + RBx + RCx = 0
- 𝑅𝐴 𝑐𝑜𝑠62 + 𝑅𝐵 𝑐𝑜𝑠65 + 𝑅𝐶 𝑐𝑜𝑠65 = 0
𝑐𝑜𝑠65
𝑅𝐴 = (𝑅 + 𝑅𝐶 )
𝑐𝑜𝑠62 𝐵
𝑐𝑜𝑠65
𝑅𝐴 = (146.96)
𝑐𝑜𝑠62
𝑅𝐴 = 132.29𝑘𝑔𝑓