Difficulty: Easy
Correct Answer: no
Explanation:
Introduction / Context:Apparent weight is the normal reaction a supporting surface exerts on a body. It can differ from true weight depending on acceleration of the reference frame. A classic case is free fall, which underpins weightlessness sensations in elevators and spacecraft in orbit.
Given Data / Assumptions:
Concept / Approach:For vertical motion with acceleration a, Newton’s second law on the body with upward positive gives: N − W = −m a (if downward acceleration). In free fall, a = g downward, so N = 0. The body is locally weightless although gravitational force W = m g still acts; what vanishes is the contact force that registers on a scale.
Step-by-Step Solution:
Write equilibrium with acceleration: N − m g = m a_y.For free fall: a_y = −g ⇒ N − m g = −m g ⇒ N = 0.Therefore, the apparent weight (scale reading) is zero—described here as “no weight”.True weight remains m g; it is just not felt or measured by the scale in free fall.Verification / Alternative check:In a falling elevator with broken cable (idealized), occupants and the floor accelerate together at g; hence no normal reaction is developed. Astronauts in orbit are in continuous free fall around Earth, experiencing microgravity (practically weightlessness).
Why Other Options Are Wrong:
Common Pitfalls:Confusing true weight (m g) with apparent weight (normal force). Only the latter vanishes in free fall.
Final Answer:no
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