Fill in the blanks with suitable words

To cause acceleration in an object the necessary factor is unbalanced_____ .

To cause acceleration in an object the necessary factor is unbalanced force.

Explanation: According to Newton’s second law whenever a force is applied on an object there will be change in the momentum of the object. And we know that the momentum is {} where v is velocity. Now, we know that the mass of the object is constant and if there is change in momentum that will be causing change in velocity. And change in velocity is called acceleration. Hence, if and only if an unbalanced force is applied on any object it will result in change of its momentum which will further results in changing its velocity. So to cause acceleration we must apply an unbalanced force.