A perfect frame is that which is composed of members just sufficient to keep it in equilibrium, when loaded, without any change in its shape. A perfect frame should satisfy the following expression:
n = 2j-3
where
n = Number of members, and
j = Number of joints.

An imperfect frame is one which does not satisfy the above equation (n = 2j — 3). The imperfect frame which has number of members (n) less than 2j – 3, is known as deficient frame. If the number of members are greater than 2j – 3, Then the imperfect frame is known redundant frame.

An imperfect frame is one which does not satisfy the above equation (n = 2j — 3). The imperfect frame which has number of members (n) less than 2j – 3, is known as deficient frame. If the number of members are greater than 2j – 3, Then the imperfect frame is known redundant frame.

Quantities which are having only magnitude but no direction are called scalar quantity.

Speed is the rate of change of displacement with respect to its surrounding. Since the speed of a body is irrespective of its direction, therefore it is a scalar quantity.

The rate of change of displacement of a body is called Velocity.
Velocity The rate of change of position of a particle in a given direction is called its velocity. Thus velocity is displacement made by the body per unit time. Velocity is a vector quantity.

Speed The rate of change of position of particle irrespective of direction is called speed. It is measured by distance covered per unit time. Speed is a scalar quantity.