Apple on a Desk - Students discuss forces acting on an apple resting on a desk.

The student I most agree with is Soledad.

Explanation:

Soledad said:
> "There are two forces: the desk pushes up on the apple and gravity pulls downward on the apple."

This statement is correct according to the principles of physics, specifically Newton’s First Law of Motion and the concept of equilibrium.

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Why Soledad is correct:

When an apple sits at rest on a desk, it is in static equilibrium, meaning:
- It is not accelerating (it's not moving).
- The net force acting on it must be zero (from Newton’s First Law).

But that doesn’t mean no forces are acting — just that the forces balance out.

#### Two main forces act on the apple:
1. Gravity (Weight): This is the force pulling the apple downward toward Earth. It acts because of the apple’s mass and the gravitational field.
2. Normal Force: This is the upward push from the desk on the apple. It is a contact force that prevents the apple from falling through the desk.

These two forces are equal in magnitude and opposite in direction, so they cancel each other out, resulting in zero net force.

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Why the others are incorrect:

- Archie: Says only air pressure acts. While air pressure does exist, it acts equally from all directions and cancels out. Air pressure is not the dominant force keeping the apple on the desk. Gravity is much more significant here.

- Sam: Says only gravity acts. That would mean the apple should accelerate downward, but it doesn't. So there must be an opposing force — the normal force from the desk.

- Misha: Mentions “holding force,” which is vague and not a standard physics term. There is no mysterious “holding force.” The force preventing the apple from falling is the normal force from the desk.

- Tess: Says there are no forces acting. This is false. Forces *are* acting — otherwise, why would the apple have weight? If no forces acted, it wouldn't even be affected by gravity.

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Rule/Reasoning Used:

I used Newton’s First Law of Motion:
> An object at rest stays at rest unless acted upon by a net external force.

Since the apple is at rest, the net force is zero, but that doesn’t mean no forces are present. We use free-body diagrams and analyze real forces:
- Gravity (down)
- Normal force (up)

These two forces are present and balanced.

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Final Answer:

✔ I most agree with Soledad.

She correctly identified the two forces acting on the apple: gravity pulling down and the desk pushing up. These forces balance, keeping the apple at rest.