Question

can a body be in equilibrium when only one force acts on it ? explain

Answer 1

No, a body can only be in equilibrium when vector sum of forces acting on it is zero. So if only one non zero force is acting on it, it can not be in kinetic equilibrium.

For example, take freely falling bodies. Only one force act on them. Your question can be framed to say "Can a apple hang in air if hold holding it?"

Which of course you can see won't happen.

Hope this helped

Answer 2

no its not possible