Question

which of the following best explains the motion of the items throughout this sequence?
a. the items only move when an unbalanced force is acting on them.
b. the items only move when a balanced force is acting on them.
c. unbalanced forces keep the items stationary when the belt is turned off.
d. the belt creates balanced forces, causing the items to speed up continuously.

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. Balanced forces result in no change in motion (either remaining stationary or moving at a constant velocity). Unbalanced forces cause a change in motion (acceleration or deceleration).

• Option A: When an unbalanced force acts on an object, its state of motion changes (it moves if it was stationary or changes its velocity if it was already moving). This is in line with Newton's first law.
• Option B: Balanced forces mean there is no net force, so the object will either remain stationary (if it was initially stationary) or move at a constant velocity (if it was already moving). It does not cause an object to start moving from a stationary state.
• Option C: Unbalanced forces cause a change in motion. When the belt is turned off, if there are unbalanced forces (e.g., friction), the items will not remain stationary (they will decelerate).
• Option D: Balanced forces do not cause an object to speed up continuously. Speeding up continuously implies an acceleration, which requires an unbalanced force.

Answer:

A. The items only move when an unbalanced force is acting on them.