Question

Which of the following is correct for balanced and unbalanced forces?
A. If set forces acting on the body results in change in state such forces are called unbalanced forces.
B. The vector sum of all forces is zero i.e. $$\sum F = 0$$
C. The object is in equilibrium and the resultant force is non-zero. i.e. $\sum {{F_x}} \ne 0$
D. All

Answer 1

Hint: A force is a pull or push on an object that results in an acceleration in the object. When two individual forces, acting on a single object, will be of equal magnitude and opposite direction, then the force will be a balanced force. On the other hand, when the forces will be not equal in magnitude and in opposite directions, then the force will be an unbalanced force.

Complete answer:
When the net force acting on the body will be zero and the acceleration will also be zero, this force will be a balanced force. Also, if the set of forces that acts on a body will not change the state of rest or the state of motion, then such force will be a balanced force. This is the case, when the object will be in equilibrium state. Also, the vector sum of all the forces will be zero. i.e. $\sum {{F_x}} = 0$

Now, when the net force acting on the body will be non-zero, then there will be acceleration in the body, this force will be an unbalanced force. Also, if the set of forces that acts on a body will change the state of rest or state of motion, then such force will be an unbalanced force. This is the case, when the object will be in a non-equilibrium state. Also, the vector sum of all the force will be non-zero. i.e. $\sum {{F_x}} \ne 0$. Therefore, from the above discussion, we can say that all the given options are correct.

Hence, option D is the correct option.

Note: Here, we will assume that the body is not massless and the mass of the body does not vary. Also, the force vector will lie anywhere in the space i.e. the force vector will not only lie in $1D$ or $2D$ but will also lie in $3D$. Also, we know that at a time, several forces can act on a body.