Buoyant force equals pressure difference times area

Steps:

• Pressure acts on the top and bottom surfaces of the cylinder.
• Upward force on bottom: p2 × A.
• Downward force on top: p1 × A.
• Net upthrust: (p2 × A) - (p1 × A) = (p2 - p1)A.

Why A is correct:

• Archimedes' principle states upthrust is the net upward force from fluid pressure, equal to (p2 - p1)A for vertical surfaces.

Why the others are wrong:

• B: Subtracts weight W, yielding net force (upthrust - W), not upthrust itself.
• C: Adds weight W, which incorrectly combines buoyancy with gravity.
• D: Identical to B, subtracts weight instead of isolating buoyant force.

Final answer: A