Mass measures the amount of matter in an object and its resistance to acceleration; it is measured in kilograms.

Weight is the gravitational force acting on an object; in SI, it is measured in newtons.

What does one newton represent in SI base units?

One newton equals one kilogram meter per second squared: $1\ \text{N}=1\ \text{kg}\cdot\text{m/s}^2$.

Free fall occurs when gravity is the only external force acting on an object.

What does weightlessness often mean in descriptions of space travel?

It often describes the experience of being in free fall, not the absence of gravity.

General physicsLesson 1 of 4 in the course Newton's Laws of Motion

Mass, Weight, Free Fall, and Gravitational Force

5 flashcards · 5 quiz questions · 5 match pairs · 5 fill-in sentences · English

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Summary

In everyday speech, people often use mass and weight as if they mean the same thing. Physics treats them as different quantities. This lesson explains what each quantity measures, how their units differ, and why weight changes with location while mass does not.

Mass is an intrinsic property of an object: it describes how much matter the object contains. In Newtonian physics, an object's mass does not change when the object moves from Earth to the Moon or into orbit. Mass is measured in kilograms (kg).

All flashcards

What is mass?: Mass measures the amount of matter in an object and its resistance to acceleration; it is measured in kilograms.
What is weight?: Weight is the gravitational force acting on an object; in SI, it is measured in newtons.
What does one newton represent in SI base units?: One newton equals one kilogram meter per second squared: $1\ \text{N}=1\ \text{kg}\cdot\text{m/s}^2$ .
What is free fall?: Free fall occurs when gravity is the only external force acting on an object.
What does weightlessness often mean in descriptions of space travel?: It often describes the experience of being in free fall, not the absence of gravity.

Quiz questions

Which equation gives the magnitude of an object's weight from its mass and local gravitational acceleration?Answer: $w=mg$
A descending object experiences both gravity and upward air resistance. What is its net force?Answer: The downward weight minus the upward air resistance.
A stone weighing 180 N near Earth's surface accelerates upward when lifted. How does the farmer's upward force compare with the stone's weight?Answer: It is greater than 180 N.
In ideal free fall near Earth's surface, with air resistance negligible, how does gravitational acceleration depend on an object's mass?Answer: It is the same for objects of different masses.
What does the pound (lb) measure in the stated context?Answer: Force.

Based on University Physics Volume 1 by William Moebs, Samuel J. Ling, Jeff Sanny (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.

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