Engineering Mechanics
Which of the following statement is incorrect?

A machine whose efficiency is 100% is known as an ideal machine
A force acting in the opposite direction to the motion of the body is called force of friction
The ratio of the limiting friction to the normal reaction is called coefficient of friction
The velocity ratio of a machine is the ratio of load lifted to the effort applied

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Engineering Mechanics
One joule means that

Work is done by a force of 1 g when it displaces a body through 1 cm
Work is done by a force of 1 kg when it displaces a body through 1 m
Work is done by a force of 1 N when it displaces a body through 1 m
Work is done by a force of 1 dyne when it displaces a body through 1 cm

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Engineering Mechanics
Varingon's theorem of moments states that if a number of coplanar forces acting on a particle are in equilibrium, then

Their lines of action are at equal distances
Their algebraic sum is zero
The algebraic sum of their moments about any point is equal to the moment of their resultant force about the same point
The algebraic sum of their moments about any point in their plane is zero

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