If you drop your textbook, it speeds up while it is falling, and therefore
A) there are no forces acting on the book.
B) all of the forces acting on the book are balanced.
C) the forces acting on the book are unbalanced.
D) none of the above

Question

Quizplus · Accepted Answer

According to Newton's second law of motion, an object will only accelerate if there is an unbalanced force acting on it. In this case, the force of gravity is pulling the book downwards while there is no other force acting on it (since air resistance is negligible for a falling book). Therefore, the forces acting on the book are unbalanced, causing it to accelerate as it falls.

If You Drop Your Textbook, It Speeds Up While It