Summary
Mass is the amount of matter in an object, while weight is the force exerted by gravity on that mass. Mass is measured in kilograms (kg) and remains constant regardless of location, whereas weight is measured in newtons (N) and can change with the gravitational field.
- Mass — the amount of matter in an object Example: A 5 kg bag of sugar has a mass of 5 kg regardless of where it is.
- Weight — the force of gravity acting on a mass Example: A 5 kg bag of sugar weighs 50 N on Earth, where gravity is 10 N/kg.
- Gravitational Field — a region where a mass experiences a force due to gravity Example: Earth's gravitational field pulls objects towards its center.
Exam Tips
Key Definitions to Remember
- Mass is the amount of matter in an object, measured in kilograms (kg).
- Weight is the force on a mass due to gravity, measured in newtons (N).
Common Confusions
- Confusing mass with weight; remember mass is constant, weight varies with gravity.
- Forgetting that weight is a force and should be measured in newtons.
Typical Exam Questions
- What is the mass of an object that weighs 100 N on Earth? Answer: 10 kg, using W = mg and g = 10 N/kg.
- How does weight change if an object is taken to the Moon? Answer: Weight decreases because the Moon's gravitational field is weaker.
- Calculate the weight of a 2 kg object on Earth. Answer: 20 N, using W = mg and g = 10 N/kg.
What Examiners Usually Test
- Understanding the difference between mass and weight.
- Ability to use the formula W = mg to calculate weight.
- Knowledge of how gravitational fields affect weight.