SSC JE Mechanical Engineering 2018 Set 2 Paper

Question : 137 of 200

Marks: +1, -0

In an Otto cycle, air is compressed from 3 litres to 2.4 litres from a starting pressure of 1.5 kg/ cm

^{2}

. The net output per cycle is 400 kJ. What is the mean effective pressure (kPa) of the cycle?

Solution:

Given:

V_1 = 3 \ltr = 3 × 10^{–3} m^3

V_2 = 2.4 \ltr = 2.4 × 10^{–3 }m^{3}

P_1 = 1.5

kg/cm

^2

w = 400 kJ
We know work done = p

_\mean

× swept volume

400 = p_m × (3 -2.4) × 10^{–3}

p_m=400/{.6×10^{–3 }}=667

kPa

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