Multiple Choice
An object of mass is launched from the surface of a planet of mass and radius . What is the minimum speed required for the object to escape the planet's gravitational field (the escape velocity)?
8. Centripetal Forces & Gravitation
Newton's Law of Gravity
Multiple Choice
In the context of Newton's law of gravity, what term refers to the measure of the force of gravity acting on an object near a planet's surface?
A
Weight
B
Inertia
C
Density
D
Mass
Verified step by step guidance1
Understand that Newton's law of gravity describes the gravitational force between two masses, given by the formula \(F = G \frac{m_1 m_2}{r^2}\), where \(F\) is the gravitational force, \(G\) is the gravitational constant, \(m_1\) and \(m_2\) are the masses, and \(r\) is the distance between their centers.
Recognize that near a planet's surface, one of the masses is the planet itself, and the other is the object experiencing the force. The force of gravity acting on the object is commonly called its weight.
Weight is defined as the force due to gravity acting on an object's mass, and it can be calculated using the formula \(W = mg\), where \(W\) is weight, \(m\) is the object's mass, and \(g\) is the acceleration due to gravity at the planet's surface.
Distinguish weight from mass: mass is the amount of matter in an object and does not change with location, while weight depends on the gravitational field strength and can vary depending on the planet or altitude.
Therefore, the term that refers to the measure of the force of gravity acting on an object near a planet's surface is 'weight'.
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