Applied Mechanics and Graphic Statics
The characteristic of a couple is:

All listed here
A couple can be never the balanced by a single force
Algebraic sum of moments of forces, constituting a couple, about any point, is same
Algebraic sum of forces, constituting a couple is zero

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Applied Mechanics and Graphic Statics
One end of an elastic string of natural length ‘l’ and modulus ‘X’ is kept fixed while to the other end is attached a particle of mass m which is hanging freely under gravity. The particle is pulled down vertically through a distance ‘x’, held at rest and then released.The motion is

A damped oscillatory motion
A simple harmonic motion
A rectilinear motion with constant speed
None of these

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