Define gravitational potential at a point - AQA - A-Level Physics - Question 3 - 2019 - Paper 2
Question 3
Define gravitational potential at a point.
0 3 . 2
Figure 2 shows the positions of equipotential surfaces at different distances from the centre of the Moon.
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Worked Solution & Example Answer:Define gravitational potential at a point - AQA - A-Level Physics - Question 3 - 2019 - Paper 2
Step 1
Define gravitational potential at a point.
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Answer
Gravitational potential at a point is defined as the work done per unit mass in bringing a small test mass from infinity to that point against the gravitational field.
Step 2
Explain how the equipotential surfaces in Figure 2 show that the gravitational field is not uniform.
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Answer
The equipotential surfaces in Figure 2 show variations in gravitational potential at different distances from the Moon's center. As the distance from the center of the Moon increases, the spacing between the equipotential surfaces decreases, indicating that the gravitational field strength changes. The non-parallel lines signify that the gravitational force is stronger closer to the Moon and weaker further away.
Step 3
Calculate, using Figure 2, the escape velocity at the surface of the Moon.
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Answer
To calculate the escape velocity (
ve
) at the surface of the Moon, we use the formula:
ve=2gh
where:
g is the gravitational acceleration at the surface, and
h is the height, which is equivalent to the radius of the Moon.
From Figure 2, we can infer g using the potential difference between equipotential surfaces:
g=−ΔrΔV
Using the values:
r=1.74×106extm
we find:
ve=2imes2.4×102extm/s2×1.74×106extm
After calculating, ve≈2.3×103extm/s.