5.15
Marcos de referencia no inercials
Un marco de referencia que está acelerando o desacelerando con respecto a un marco de referencia inercial es un marco no inercial. Para entender esto,…
Recordemos que los marcos de referencia en los que se cumplen las leyes de Newton se conocen como marcos inerciales. Sin embargo, hay marcos de referencia que desafían las leyes de Newton, llamados marcos de referencia no inerciales.
Los bastidores no inerciales aceleran o desaceleran en relación con los bastidores inerciales.
Por ejemplo, cuando un avión despega, los pasajeros sienten una fuerza hacia atrás opuesta a la aceleración del avión. Esto viola la segunda ley de Newton según la cual los objetos se aceleran en la dirección de la fuerza externa neta.
En los marcos no inerciales, las fuerzas inerciales o ficticias que no tienen origen físico son necesarias para explicar el movimiento de los objetos. Entonces, en mecánica, es más conveniente usar un marco inercial.
Idealmente, un marco de referencia fijado a la Tierra no es inercial debido a su revolución y rotación. Sin embargo, las fuerzas debidas a la rotación de la Tierra son insignificantes en pequeños movimientos mecánicos, pero afectan a movimientos a gran escala como los patrones de viento.
La fuerza ficticia en este marco desvía el viento en el sentido de las agujas del reloj en el hemisferio norte y en el sentido contrario a las agujas del reloj en el hemisferio sur.
Q1: What is the difference between inertial and non-inertial reference frames?
Inertial frames are reference frames where Newton's laws hold true. Non-inertial frames are either accelerating or decelerating relative to inertial frames, causing Newton's laws to appear violated. In non-inertial frames, fictitious forces with no physical origin must be introduced to explain object motion, making inertial frames more convenient for mechanical analysis.
Q2: Why do passengers feel pushed backward when an airplane accelerates?
Passengers in an accelerating airplane experience a fictitious force pushing them backward, opposite to the plane's acceleration. This apparent force arises because the airplane cabin is a non-inertial frame accelerating relative to Earth. From an inertial frame perspective, passengers tend to maintain their original motion due to inertia while the plane accelerates forward beneath them.
Q3: What are inertial forces and why do they appear in non-inertial frames?
Inertial forces are fictitious forces that appear to arise from motion in non-inertial frames but have no identifiable physical source. They exist only because the observer's frame of reference is accelerating or rotating. These forces allow Newton's second law to be applied in accelerated frames, though using an inertial frame eliminates the need for such invented forces.
Q4: How does Earth's rotation affect weather systems like hurricanes?
Earth's rotation creates a fictitious Coriolis force in the non-inertial frame of Earth's surface. This force deflects wind clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere, causing hurricanes to rotate counterclockwise in the north and tropical cyclones to rotate clockwise in the south. Although Earth's angular velocity is small, this effect significantly impacts large-scale weather patterns.
Q5: Can Earth be treated as an inertial reference frame for everyday mechanics?
Yes, Earth can be used as an inertial frame for small mechanical motions with negligible effects from rotation. However, for large-scale phenomena like wind patterns and tropical cyclones, Earth's rotation produces measurable fictitious forces that must be considered. The choice of reference frame depends on the scale and precision required for the analysis.
Q6: How do physicists choose between inertial and non-inertial reference frames?
Physicists select the reference frame most convenient for analyzing a specific situation. Inertial frames are simpler because all forces have identifiable physical sources and Newton's laws apply directly. Non-inertial frames are useful when they simplify calculations, though they require introducing fictitious forces. The choice depends on which perspective makes the problem easier to solve.
Q7: What common experiences demonstrate non-inertial reference frames?
Taking off in an airplane, turning a corner in a car, riding a merry-go-round, and observing tropical cyclone motion all occur in non-inertial frames. These systems are accelerating, decelerating, or rotating relative to Earth, exhibiting inertial forces that seem to arise from motion. Understanding these everyday examples helps clarify how reference frame choice affects our perception of forces and motion.