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Accélération due à la gravité sur Terre
La deuxième loi de Newton est étroitement liée à sa première loi du mouvement. Elle donne mathématiquement la relation de cause à effet entre la force…
Prenons l’exemple d’une dame qui pousse un chariot à bagages pendant qu’elle se déplace. La force externe exercée par elle accélère le chariot dans la direction de la force appliquée.
Si elle pousse avec une force plus grande, le chariot se déplacera plus rapidement. Pour arrêter le chariot, elle doit appliquer une force externe dans la direction opposée à son mouvement.
Si elle place plus de bagages sur le chariot, la même force produit une accélération plus faible dans la direction de la force externe nette.
En les compilant, nous obtenons la deuxième loi du mouvement de Newton, qui stipule qu'un objet accélère proportionnellement et dans la direction de la force externe nette et inversement à sa masse.
Ou encore, la force externe nette agissant sur un objet est le produit de sa masse et de son accélération. Tous les objets en accélération suivent la deuxième loi de Newton.
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Q1: What is acceleration due to gravity on Earth?
Acceleration due to gravity is the rate at which objects accelerate toward Earth's surface when falling freely under gravitational force alone. On Earth, this value is approximately 9.8 meters per second squared (m/s²). This constant applies to all objects regardless of mass, making it a fundamental constant in physics and mechanics.
Q2: Why does gravitational acceleration remain constant near Earth's surface?
Gravitational acceleration is constant near Earth's surface because the gravitational force acting on an object is proportional to its mass, and this force divided by mass yields a constant value. The distance from Earth's center remains relatively unchanged at the surface, so the acceleration remains approximately 9.8 m/s² for all objects in free fall.
Q3: How does mass affect an object's acceleration due to gravity?
Mass does not affect an object's acceleration due to gravity. Although gravitational force increases with mass, the acceleration remains constant at 9.8 m/s² because force and mass are proportionally related. This means a feather and a bowling ball accelerate at the same rate when falling freely in a vacuum.
Q4: What is the relationship between weight and gravitational acceleration?
Weight is the gravitational force exerted on an object and is calculated by multiplying mass by gravitational acceleration (W = mg). Since gravitational acceleration on Earth is 9.8 m/s², an object's weight increases proportionally with its mass. Weight varies with location, while mass remains constant.
Q5: How does altitude affect gravitational acceleration on Earth?
Gravitational acceleration decreases slightly with increasing altitude because distance from Earth's center increases. At higher elevations, objects experience slightly less gravitational acceleration than the standard 9.8 m/s² at sea level. This effect becomes more pronounced at extreme altitudes, such as in space or on mountains.
Q6: Why is gravitational acceleration important in mechanical engineering calculations?
Gravitational acceleration is essential for calculating forces, motion, and energy in mechanical systems. Engineers use the 9.8 m/s² value to determine structural loads, design safety systems, and predict object motion. Accurate gravitational acceleration values ensure reliable predictions of system behavior and component performance.