For machines

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Example 4:

An effort of 250N raises a load of 1000N through 5m in 10 seconds. If the velocity ratio is five, Calculate the:

i) Power input

ii) Efficiency

Solution:

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Internal combustion engine

A heat engine is a machine, which changes heat energy obtained by burning fuel to kinetic energy (mechanical energy)
Engines are always less than 100% efficient because:-
i) Some of the energy is lost in over coming friction between walls of the cylinder and pistons.
ii) Some heat energy is lost to surrounding due to conduction.