Answer:
Unbalanced force
Step-by-step explanation:
According to Newton's second law of motion, any unbalanced force that is applied on a body will cause it to have some acceleration.
However, If the force is balanced like the net effect of one force is cancelled by the other, it will result in total force as zero, that will cause zero acceleration in the body.
Newton's second law of motion states:
F=ma
where m is mass and a is acceleration, so it means that is any of these factors is zero , the force will be zero, and hence force is zero only when it is cancelled by some force acting in opposite direction.
For example: When person is dragging the table with a force of 30 N on left side, while the other person is dragging the same table with same force on right side. The table will have zero acceleration.
Hope it help!