Final answer:
The modeling clay figure toppled over backward because of Newton's first law, or the law of inertia, which states that an object will maintain its state of rest or uniform motion unless acted upon by an unbalanced force.
The correct answer is 1) Newton's first law.
Step-by-step explanation:
Understanding the Physical Principle Behind the Toppling Clay Figure
The physical principle that explains why the modeling clay figure toppled over backward when the lab cart was hit by another of equal mass is Newton's first law of motion. This law, also known as the law of inertia, states that an object at rest will stay at rest, and an object in motion will stay in motion with the same speed and in the same direction unless acted upon by an unbalanced external force.
The inertial force experienced by the clay figure when the stationary cart suddenly moved caused it to topple over. The sudden start of motion of the cart was an unbalanced force that changed the state of rest of the clay figure. However, due to inertia, the bottom part of the figure, being in contact with the cart, was forced to move along with the cart, while the top part naturally tended to remain in its initial state of rest. This discrepancy in motion between the bottom and top of the figure led to it toppling over backward.
Considering that the clay figure represents a system initially at rest, it experienced no net force before the collision. Once the collision occurred, the external force applied by the second cart caused the cart with the clay figure to accelerate. Since the clay figure was unsecured, its tendency to remain at rest caused it to topple over as the cart began to move. This effect can be compared to a ruler plucked and released, which oscillates due to restoring forces, providing a simple example of how forces lead to changes in motion.
The correct answer is 1) Newton's first law.