Question

Which of these would be an example of unbalanced forces?

A. You stand very still during the National Anthem.

B. Your coffee cup does not move from its original spot on the desk.

C. A dog runs at a constant velocity.

D. A snowball picks up speed as it rolls down the mountain.

Answer 1

Your answer is:

D. A snowball picks up speed as it rolls down the mountain.

An unbalanced force is when 2 forces act on each other (they aren't equal and opposite). That makes them cause motion.

Answer 2

A snowball picks up speed as it rolls down the mountain. (D)

Since the description includes acceleration ("picks up speed"), we know that the forces on the snowball must be unbalanced.