(a)
a) Choose a heavy object like a table or a box, which you can move only by pushing hard.
b) Try to push it all by yourself. Can you move it?
c) Now ask one of your friends to help you in pushing it in the same direction.
d) Is it easier to move it now? Can you explain why? Next, push the same object, but ask your friend to push it from the opposite side.
e) Does the object move? If it does, note the direction in which it moves. Can you guess which one of you is applying a larger force?
(b)
i. The forces acting on the suitcase are unbalanced. The air friction, weight & the airspeed are acting on the ball.
Example, the figure is given below:

ii. Balanced forces.
iii. There are balanced forces.