IGCSE 0625 · MECHANICS · 1.3

Mass and weight

The difference between mass and weight, the equation W = mg, and gravitational field strength. It builds on physical quantities and feeds into forces and energy.

TOPIC 1.3: MASS AND WEIGHT CAMBRIDGE IGCSE PHYSICS 0625 · PATHWAYS TheLucidSTEM · thelucidstem.com BUILDS ON 1.1 Quantities LEADS TO 1.5 Forces 1.7 Energy MASS & WEIGHT 1 · MASS Mass is the amount of matter in an object. Measured in kilograms (kg) with a balance. The same everywhere, on Earth or the Moon. More mass means more resistance to a change in motion. We call this inertia. 2 · WEIGHT Weight is the gravitational force pulling on a mass. W = m g g = field strength Measured in newtons (N). It changes if gravity changes with location. 3 · GRAVITATIONAL FIELD STRENGTH g is the gravitational force on each kilogram. g = W / m in newtons per kilogram (N/kg) The same mass weighs less where g is smaller: on Earth g ≈ 9.8 N/kg on the Moon g ≈ 1.6 N/kg same mass, smaller weight on the Moon 4 · MASS vs WEIGHT They are linked but not the same. MASS amount of matter scalar quantity unit: kilogram (kg) stays constant found with a balance WEIGHT force of gravity vector quantity unit: newton (N) varies with g found from W = mg
TOPIC 1.3: MASS AND WEIGHT CAMBRIDGE IGCSE PHYSICS 0625 · PATHWAYS TheLucidSTEM · thelucidstem.com BUILDS ON 1.1 Quantities LEADS TO 1.5 Forces 1.7 Energy MASS & WEIGHT 1 · MASS Mass is the amount of matter in an object. Measured in kilograms (kg) with a balance. The same everywhere, on Earth or the Moon. More mass means more resistance to a change in motion. We call this inertia. 2 · WEIGHT Weight is the gravitational force pulling on a mass. W = m g g = field strength Measured in newtons (N). It changes if gravity changes with location. 3 · GRAVITATIONAL FIELD STRENGTH g is the gravitational force on each kilogram. g = W / m in newtons per kilogram (N/kg) The same mass weighs less where g is smaller: on Earth g ≈ 9.8 N/kg on the Moon g ≈ 1.6 N/kg same mass, smaller weight on the Moon 4 · MASS vs WEIGHT They are linked but not the same. MASS amount of matter scalar quantity unit: kilogram (kg) stays constant found with a balance WEIGHT force of gravity vector quantity unit: newton (N) varies with g found from W = mg
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