8.01x - Lect 7 - Weight, Weightlessness in Free Fall, Weight in Orbit
Lectures by Walter Lewin. They will make you ♥ Physics.・2 minutes read
The lecture focuses on weight, defined as the force exerted on an object by gravity, with examples of weight changes in different scenarios, such as free fall and acceleration in elevators, using Newton's Second Law and tension in strings. Zero gravity experiments on airplanes like the KC-135 study motion sickness under weightless conditions, with participants alternating between weightlessness and increased weight every 90 seconds.
Insights
- Weight is directly linked to mass and gravity, with the force exerted on an object by gravity defining its weight, as seen in scenarios like elevator accelerations and free fall.
- Tension in a string can indicate weight, remaining constant in a frictionless system, with acceleration affecting weight readings, leading to situations like objects of different masses having the same weight when suspended.
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Recent questions
What is weight?
Weight is the force exerted on an object by gravity, often measured on a bathroom scale. It is directly related to an object's mass and the force of gravity acting upon it.
How does acceleration affect weight?
Acceleration can impact an object's weight. When accelerating upwards in an elevator, the force from the scale must exceed gravity for acceleration to occur, increasing weight. Conversely, accelerating downwards results in decreased weight as the scale force is less than gravity.
What is free fall?
Free fall occurs when acceleration due to gravity cancels out, resulting in weightlessness and a reading of zero on the scale. During free fall, all objects are weightless, like in a spacecraft in orbit or an elevator with a cut cable.
How is tension in a string related to weight?
Tension in a string can indicate weight, with tension increasing when accelerating upwards and decreasing when accelerating downwards. The tension remains constant due to the absence of friction and the masslessness of the string.
What happens during zero gravity experiments?
Zero gravity experiments are conducted on airplanes like the KC-135 at high altitudes, creating a cycle of free fall, increased weight, normal weight, and weightlessness every 90 seconds. Participants experience weightlessness and increased weight alternately to study motion sickness under such conditions.
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