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Magazine Chapter 4: Problem 29
Which person is weightless? (a) a child in the air as she plays on a trampoline (b) a scuba diver exploring a deep-sea wreck (c) an astronaut on the Moon
Short Answer
Expert verified
The child in the air playing on a trampoline is weightless.
Step by step solution
01
Understanding Weightlessness
Weightlessness occurs when a person or object is in free fall, experiencing no net force acting upon them except gravity. This means they do not have any support force or other forces such as buoyancy opposing gravity, leading to a sensation of weightlessness.
02
Analyzing the Child on the Trampoline
When a child is in the air after jumping on a trampoline, they are briefly in free fall as gravity is the only force acting on them during this time. Thus, the child experiences a moment of weightlessness while in the air.
03
Analyzing the Scuba Diver
A scuba diver is under water, and while they may experience a sensation of being lighter due to buoyancy, they are not weightless. The diver is not in free fall since the buoyant force and the water pressure balance some of the force of gravity.
04
Analyzing the Astronaut on the Moon
An astronaut on the Moon experiences reduced gravity compared to Earth, but they are not weightless. The Moon's gravitational pull is still acting on them, which means they have weight, albeit less than on Earth. They would float if not tethered, but this is not the true sensation of weightlessness.
05
Conclusion
Based on the analysis, the child on the trampoline is the only person who experiences true weightlessness, albeit momentarily, when they are in free fall.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Gravity
Gravity is a fundamental force of nature that attracts two bodies toward each other. It is what keeps the planets in our solar system in orbit around the Sun and causes objects to fall towards the Earth when dropped. The force of gravity is dependent on the mass of the objects and the distance between them. We usually feel gravity as the force that gives us weight, pulling us towards the Earth. This force is counteracted by the surface we stand on, which provides an opposite upward force called the normal force. Thus, when we talk about being weightless, we refer to a situation where the only force acting on us is gravity, without any supporting or counteracting forces.
Free Fall
Free fall is a condition in which the only force acting on an object is gravity. During free fall, an object accelerates downward at the acceleration due to gravity, which is approximately 9.8 m/s虏 on Earth. Free fall creates the sensation of weightlessness because there is no upward force countering gravity.
- A person in free fall experiences no resistance or support from solid surfaces.
- This state is temporary unless in a vacuum because air resistance will soon play a role, reducing the sensation of weightlessness.
Buoyancy
Buoyancy is a force that acts in the opposite direction of gravity. This force is what allows objects to float in fluids, such as water or air. It arises due to the pressure differences in the fluid, which pushes the object upward.
- The strength of buoyancy depends on the volume of the object and the density of the fluid.
- In water, the force of buoyancy makes many objects feel lighter, including humans when they swim or dive.
Space Exploration
Space exploration involves traveling beyond Earth's atmosphere to understand more about space and celestial bodies. In this environment, the absence of air and decreased gravitational pull create unique conditions.
- Astronauts often experience weightlessness when they are in orbit because they are essentially in a continuous state of free fall around Earth.
- The concept of weightlessness is central to many experiments conducted in space, helping us understand biological and physical phenomena unobserved on Earth.
