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A motor cycle engine delivers a power of `10 kW`, by consuming petrol at the rate of `2.4 kg//hour`. If the calorific value of petrol is `35.5 MJ//kg`, the rate of heat rejection by the exhaust byA. `5.5 kW`B. `13.7 kW`C. `11.2 kW`D. `9.7 kW` |
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Answer» Correct Answer - B Heat recived (or produce by the burning of petrol) in one hour will be `=(2.4 kg//hour) (3.5 MJ//kg)` `=85.2xx10^(6)J//hour` `:.` The rate at which heat is recevied ltbr. `=(85.2xx10^6 J)/((3600s)) = 2.37xx10^(4) J//s = 23.7kW` Evidently the rate of heat rejection =rate at which heat is produced - rate at which work is obtained = `23.7kW - 10kW = 13.7kW`. |
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