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Mass, Weight, Density and Pressure

Quick questions on Mass and weight explained: O-Level Physics

6short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.

What is mass?
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Mass is the amount of matter in an object. It is a scalar, measured in kilograms (kg\text{kg}), and it does not change when the object is moved to the Moon, into space, or up a mountain. Mass also measures inertia, the reluctance of an object to change its motion.
What is weight?
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Weight is the gravitational force acting on an object. It is a vector pointing downward (toward the centre of the Earth), measured in newtons (N\text{N}):
What is gravitational field strength?
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The gravitational field strength gg is the force of gravity on each kilogram of mass:
What is q1?
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State the difference between mass and weight, including their units. [2 marks]
What is q2?
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A box has a mass of 12 kg12\ \text{kg}. Find its weight on Earth, where g=10 N kg1g = 10\ \text{N kg}^{-1}. [2 marks]
What is q3?
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Explain why an astronaut weighs less on the Moon than on Earth but has the same mass. [3 marks]

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