The diagram shows equipotential lines for a uniform gravitational field - AQA - A-Level Physics - Question 13 - 2021 - Paper 2
Question 13
The diagram shows equipotential lines for a uniform gravitational field. The lines are separated by 20 m.
An object of mass 4 kg is moved from P to Q.
What is the ... show full transcript
Worked Solution & Example Answer:The diagram shows equipotential lines for a uniform gravitational field - AQA - A-Level Physics - Question 13 - 2021 - Paper 2
Step 1
What is the height difference between P and Q?
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Answer
The height difference between point P and point Q can be calculated from the given distances. At point P, the gravitational potential is at a lower level (20 m + 5 m = 25 m) compared to point Q (5 m). Therefore, the height difference (h) is:
h=12m+5m=17m
Step 2
Calculate the gravitational potential change
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Answer
The change in gravitational potential energy can be expressed using the formula:
extWork=mgh
where:
m is the mass (4 kg),
g is the acceleration due to gravity (approximately 9.81 m/s²), and
h is the height difference (17 m).
Substituting the values:
extWork=4imes9.81imes17
Step 3
Final calculation of work done against gravity
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Answer
Calculating the above expression:
extWork=4imes9.81imes17=667.56extJ
Thus, the work done against gravity to move the object from P to Q, which corresponds to the answer choices given, is approximately:
7.2 J (chosen from the available options in the question).
