Exam-style question
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What is the gravitational field strength at a distance of 2r from a mass M, compared to that at distance r?.
- A.It is four times weaker
- B.It is twice as strong
- C.It is the same
- D.It is half as strong
Model answer
What a good answer should say
- It is four times weaker
Explanation
Why this works
Gravitational field strength g is given by g = GM/r^2. If the distance is doubled (2r), the field strength becomes g' = GM/(2r)^2 = GM/(4r^2) = g/4, indicating that the gravitational field strength is four times weaker at distance 2r.
Common mistake
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