We are asked to fill in the blanks with the correct terms.
Q.1:
Recall that the rate of change of velocity is called acceleration.
Or in other words,
Acceleration is the rate at which the velocity changes.
Q.2:
When all the forces acting upon an object are balanced then the object is said to be in equilibrium.
Or in other words,
Equilibrium is the condition in which all forces balance.
Q.3:
The net force is the vector sum of all the forces acting on an object.
Or in other words,
The sum of all forces on an object is the net force.
Consider any object in your surroundings, like a book on a table.
There are several forces acting on the book.
The force of gravitation is pulling the book downward and the force of friction is pushing it upward.
When you add up all these forces, the result will be called net force.
Summary:
Q.1: Acceleration
Q.2: Equilibrium
Q.3 Net force