A steel ball bearing is dropped into a viscous liquid and falls at its terminal velocity. Which statement is correct about the net force on it?
Answer and explanation
Correct answer: C. The net force is zero
- Step 1: Terminal velocity means constant velocity.
- Step 2: By Newton's first law, constant velocity requires a zero net force: weight is balanced by drag plus upthrust.
Answer
The net force is zero.
Why not the others: The net force acts upwards and equals the weight: would decelerate the ball. The net force acts downwards and equals the drag: would accelerate the ball. The net force is equal to the upthrust alone: ignores the weight and drag, which are also acting.
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