Label these as balanced or unbalanced:
1. a book lying on a table
2.an airplane cruising in level flight
3.a rock falling from a cliff
4.a bridge collapsing in an earthquake
5.a man sitting on a park bench
6.a space shuttle taking off
7.a car maintaining a constant speed on a straight road
8.an airplane landing

Explanation:

Usually, one or more forces act on a body at an instant of time. When these forces acting on a body and bring the body in the equilibrium position, the force is said to be balanced. The unbalanced force changes the equilibrium state of the body.

As in the case of an airplane cruising in a level flight, the weight of the plane will be equal to the lift force and the thrust is equal to the drag. So the plane is experiencing a balanced force.

and 1and 1