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If the 30 N on the rope were pulled straight up, it would offset the force of gravity ( m g = 10 kg * 9.8 N/kg = 98 N) , leaving a net force up from the ground on the sled of 98-30 = 68 N. Since the rope is pulled at the angle of 25o, only part of the force is in the upward direction, (30N)(sin(25) = (30)(.423) = 12.7. So the net force becomes 98 N down offset by 12.7 up or 98-12.7 = 85.3 N. Ah, there it is: C.
Answer:
Final temperature is equal to 1291.63°R
Explanation:
given,
p₁ = 100 lb f/in², v₁ = 3.704 ft³/lb, and T₁ = 1000 °R
p₂ = 30 lb f/in² n = 1.4
Δ u = 0.171(T₂ - T₁)
we know for poly tropic process
p vⁿ = constant
p₁ v₁ⁿ = p₂ v₂ⁿ
100 × 3.704¹°⁴ = 30 × v₂¹°⁴
v₂ = 8.753 ft³/lb
work done for poly tropic process
W = 
= 
= 269.525 lbf/in².ft³
W =
Btu/lb
= 49.87 Btu/lb
in the piston cylinder arrangement air is expanding acrobatically
Δ q = Δu + w
Δ u = - w
0.171(T₂ - T₁) = -49.87
0.171(T₁ - T₂) = -49.87
0.171 T₂ = 0.171 × 1000 + 49.87
T₂ = 1291.63 °R
Final temperature is equal to 1291.63°R