Answer:
A. Balanced forces do not cause a change in motion.
Explanation:
Forces on an object defines how it moves. Forces affect the motion of an object. Forces might slow the speed of an object or make it move faster. It might change the direction of motion of the object. But not always.
Balanced Forces:
When multiple forces are acting on an object but their sum is equal to zero or they cancel out each other.
Net Force = 0
Unbalanced Forces:
When multiple forces are acting upon an object and they are not balanced, they will cause a change in the motion of the object.
Newton's First Law states that an object will remain at rest or in uniform motion in a straight line unless acted upon by an external force. This law reinforces our statement that "balanced forces do not cause a change in motion."
Do gravity always cause a change in motion?
Consider an object in air or rolling down a steep surface. Also consider a book placed on a table.
Gravity is acting upon the objects in both cases. The difference is that there is a normal force on the book placed on the table which is balancing the gravitational force. Thus the forces are balanced and there is no change in motion. However, no forces are there to balance the gravitational force acting upon a falling object and thus it gains acceleration.
