Mass, Weight and Free Fall
Learning the difference between mass and weight, and the concept of free fall.
Core concept
Free fall describes the motion of an object falling under the influence of gravity alone, with no other forces (like air resistance) acting on it — in a true vacuum, all objects fall at the same rate regardless of their mass, since gravitational acceleration (approximately 9.8 m/s² on Earth) affects all masses equally. In reality, air resistance often makes lighter or less streamlined objects, like a feather, fall slower than denser objects like a stone, unless the fall occurs in a vacuum.
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Quick notes
• Mass = amount of matter (constant everywhere); Weight = force due to gravity (W = mg, varies by location).
• Weight differs on the Moon versus Earth because gravity differs, even though mass is unchanged.
• Free fall: motion under gravity alone, with all objects falling at the same rate in a vacuum.
• Air resistance causes lighter/less streamlined objects to fall slower in real (non-vacuum) conditions.