A student used a video camera to record another student dropping a marble through water in a graduated cylinder. The students watched the video in slow motion and made the observations shown below.

Question

During which part or parts of the marble’s fall did the marble experience unbalanced forces?

A
Part 1 only
B
Parts 1 and 2 only
C
Part 3 only
D
Parts 2 and 3 only

Answer 1

To determine during which part or parts of the marble's fall it experienced unbalanced forces, we need to consider the forces acting on the marble throughout its descent.

1. Part 1: When the marble is first dropped, it is acted upon by gravity. Since the marble is initially at rest, gravity is the only force acting on it, causing it to accelerate downwards. Therefore, there are unbalanced forces acting on it.

2. Part 2: As the marble moves through the water, it experiences both the force of gravity pulling it down and the buoyant force acting upwards (as well as drag force from the water). If the marble is accelerating downwards and not at terminal velocity, the forces are unbalanced.

3. Part 3: Eventually, the marble will reach a point called terminal velocity, where the forces acting on it (gravity downward and water resistance upward) become balanced, meaning it will stop accelerating and move at a constant speed. At this point, there are no unbalanced forces.

Thus, the marble experiences unbalanced forces in Part 1 and Part 2 but not in Part 3.

The correct answer is B: Parts 1 and 2 only.