5.7
Masa y Peso
La masa y el peso a menudo se usan indistintamente en la conversación cotidiana. Por ejemplo, los registros médicos a menudo muestran nuestro peso en…
La masa de un objeto es una medida de la cantidad de materia que contiene y depende del número de átomos que contiene.
Su peso es la fuerza gravitacional que actúa sobre él desde un objeto más grande, como la Tierra o la Luna, el que esté más cerca de él.
Como la cantidad de materia no cambia en respuesta a la fuerza aplicada, la masa del objeto permanece constante.
Sin embargo, su peso depende de su ubicación. Un objeto en la Tierra pesa de manera diferente al de Marte o la Luna, pero su masa sigue siendo la misma. El cambio de peso se debe a la diferencia de aceleración debido a la gravedad que actúa sobre ella.
La masa nunca puede ser cero, pero el peso se convierte en cero cuando la fuerza gravitacional no actúa sobre él. Usando esta observación y la segunda ley de Newton, un objeto de masa m pesa m por el vector g.
Es decir, cuanto mayor es la masa de un objeto, mayor es su peso. La masa es una cantidad escalar, pero el peso es un vector dirigido hacia el centro de la Tierra.
Q1: What is the difference between mass and weight in physics?
Mass measures the amount of matter in an object and remains constant regardless of location. Weight is the gravitational force acting on that mass, calculated as mass times the acceleration due to gravity. While mass is a scalar quantity, weight is a vector directed toward Earth's center. Understanding this distinction is crucial for applying newton s second law correctly.
Q2: Why does an object weigh differently on the Moon than on Earth?
Weight depends on the local acceleration due to gravity, which differs between celestial bodies. The Moon's gravity is only 1.67 m/s² compared to Earth's 9.8 m/s², so a 1.0 kg mass weighs 9.8 N on Earth but only 1.7 N on the Moon. The object's mass remains unchanged; only the gravitational force acting on it varies.
Q3: Can an object have zero weight but still have mass?
Yes. Weight becomes zero when gravitational force does not act on an object, such as in deep space far from any celestial body. However, the object's mass never becomes zero because it always contains matter. This demonstrates that mass and weight are fundamentally different physical properties.
Q4: How is weight calculated using Newton's second law?
According to Newton's second law, weight equals mass multiplied by the acceleration due to gravity, expressed as W = m × g. The greater an object's mass, the greater its weight. This relationship shows that weight is directly proportional to mass when gravity remains constant.
Q5: Why do medical records incorrectly list weight in kilograms instead of newtons?
In everyday conversation, mass and weight are used interchangeably, leading to this common error. Medical records show mass in kilograms when they should display weight in newtons, the correct unit of force. This confusion arises because most daily experiences occur on Earth's surface, where weight variations are minimal.
Q6: Is mass an intrinsic property of an object?
Yes, mass is an intrinsic property representing the quantity of matter in an object. It depends on the number of atoms present and does not change with location or applied force. This makes mass fundamentally different from weight, which varies based on gravitational conditions.
Q7: What happens to weight when an object is dropped?
When dropped, an object accelerates toward Earth's center due to gravitational force, which is its weight. If air resistance is negligible, the net force equals the gravitational force acting on the object. This acceleration demonstrates how weight, as a force, directly causes motion according to Newton's laws.