A scientist uses a balance to compare the masses of two metal cylinders on Earth. The scientist then travels to a space station orbiting a distant planet, where the gravitational field strength is much greater than on Earth, and repeats the comparison using the same balance. Explain why the balance still gives the same result for both cylinders at the space station as it did on Earth.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
Mass is a measure of the amount of matter in an object and does not change with location.
Weight is the gravitational force on a mass and therefore depends on the gravitational field strength.
In the space station both cylinders are in a stronger gravitational field, so each weight increases by the same factor.
A balance compares the weights of two objects; because both weights change by the same factor, the ratio of the weights remains unchanged and the balance gives the same reading as on Earth.
Weight is the gravitational force on a mass and therefore depends on the gravitational field strength.
In the space station both cylinders are in a stronger gravitational field, so each weight increases by the same factor.
A balance compares the weights of two objects; because both weights change by the same factor, the ratio of the weights remains unchanged and the balance gives the same reading as on Earth.
Examiner tips
- Use the terms ‘mass’ and ‘weight’ correctly; explain that mass is invariant. Show that the weight of each cylinder increases by the same factor. State that a balance measures weight, so the unchanged ratio gives the same result.
Common mistakes
- Confusing mass with weight. Failing to mention that the weight change is proportional for both cylinders. Claiming the balance measures mass directly instead of weight.
Mark scheme (4 marks)
- Mass is a measure of how much matter is in an object / mass does not change with location
- Weight is the gravitational force on a mass / weight depends on gravitational field strength
- Both cylinders experience the same (greater) gravitational field strength, so both weights increase by the same factor / the ratio of their weights remains the same
- A balance compares weights (or masses) of two objects, and since both weights change by the same factor, the balance still reads the same / the comparison is unaffected
Key terms in this question
mass · gravitational field strength · balance
Related
- All Cambridge International IGCSE Physics (0625) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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