Final answer:
An object at rest with an unbalanced force acting on it is expected to start moving or accelerate in the direction of the force, due to Newton's first law of motion or the law of inertia.
Step-by-step explanation:
If an object sits at rest with an unbalanced force acting on it, we expect it to change its state of motion. According to Newton's first law of motion, also known as the law of inertia, an object at rest will remain at rest unless acted upon by a net external force. Therefore, if there is an unbalanced force, the object will start to accelerate in the direction of the force. This is because inertia, which is related to the mass of the object, is the tendency of an object to resist changes to its state of motion.
For instance, imagine plucking a plastic ruler held at one end; it oscillates due to the restoring force created when it's deformed. Similarly, an object at rest will start moving if there is an unbalanced force; it won't stay at rest.
An example to illustrate this concept is the marble in the bowl. If the bowl is right-side up and the marble is slightly disturbed, it oscillates around the stable equilibrium. However, if the bowl is upside down and the marble is disturbed at the unstable equilibrium point, it will roll off the bowl since any slight force causes it to move away from that point. This shows that even a small unbalanced force can change the state of an object's motion.