In which of the following cases would you feel weightless?
while accelerating downward in an elevator
while falling from a roof
while walking on the Moon
while parachuting from an airplane
The Correct Answer and Explanation is:
The correct answer is: while accelerating downward in an elevator.
Explanation:
Feeling weightless occurs when there is no normal force acting on your body — that is, when you are in free fall or accelerating downward at the same rate as gravity, so you don’t feel the usual “push” from a surface supporting you.
Let’s analyze each case:
- While accelerating downward in an elevator:
If the elevator cable breaks or the elevator accelerates downward at the acceleration due to gravity (about 9.8 m/s²), you and the elevator fall together. Since both you and the elevator are accelerating downward at the same rate, you experience free fall conditions and no normal force is exerted on you by the elevator floor. This causes you to feel weightless, similar to astronauts in orbit. The sensation is like floating or falling with no resistance. - While falling from a roof:
When you fall freely under gravity (ignoring air resistance for simplicity), you also experience free fall, meaning you are accelerating downward at gravity’s acceleration and feel weightless. So, technically, you would feel weightless while falling from a roof, but the problem here is that you are accelerating downward due to gravity alone, without a supporting surface pushing against you. - While walking on the Moon:
You do not feel weightless on the Moon; you feel lighter because the Moon’s gravitational acceleration is about 1/6th that of Earth (about 1.62 m/s²), but you still feel your weight since the Moon’s surface pushes up on your feet with a normal force. Weightlessness requires no normal force, so walking on the Moon means you feel lighter, not weightless. - While parachuting from an airplane:
When you parachute, you feel some weight because the parachute slows your fall, producing air resistance, which counteracts gravity partially. The normal force is replaced by the tension in the parachute, but you do not feel weightless — you still feel your weight, although less than if you were standing still on the ground.
Summary:
Weightlessness occurs when you are in free fall or accelerating downward at the same rate as gravity, and there is no normal force acting on you. This happens in a freely falling elevator or while falling from a roof (ignoring air resistance). Walking on the Moon makes you feel lighter but not weightless, and parachuting creates air resistance, so you still feel weight.
Between the options given, the textbook example of feeling weightless is accelerating downward in an elevator (if it falls freely).