Question

an object is seen to either speed up, slow down, or change direction. what are these behaviors caused by? a balanced set of forces stable factors frictional force unbalanced forces

Explanation:

According to Newton's first law of motion, an object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force. When an object speeds up, slows down, or changes direction, its state of motion is changing. This change in motion (acceleration) is caused by unbalanced forces. Balanced forces result in no change in motion. Stable factors is a very vague term and not a scientific cause for the described motion changes. Frictional force is a type of force, but it's the unbalanced nature of forces (could include frictional force as part of an un - balanced force system) that causes the change in motion.

Answer:

unbalanced forces