Gravitational potentialAQA A-Level Physics: Flashcards

What these 12 flashcards ask

Define gravitational potential at a point.
What is the value of gravitational potential at infinity?
Why is gravitational potential negative?
What is the unit of gravitational potential?
Write V for a point or spherical mass.
Is potential a scalar or a vector?
State the equation for work done in a potential difference.
What is an equipotential surface?
What shape are equipotentials around a sphere?
Why is no work done moving along an equipotential?
How is g related to the V–r graph?
How can ΔV be found from a g–r graph?

Exam questions on Gravitational potential

A space agency is planning to lift a probe of mass 1200 kg away from the Earth. Treat the Earth as a uniform sphere of mass 5.97 × 10²⁴ kg and radius 6.37 × 10⁶ m.
The probe is moved between two points in the Earth's field, where the potentials are −6.25 × 10⁷ J kg⁻¹ and −5.80 × 10⁷ J kg⁻¹. Calculate the work that must be done on the probe by an external force.2 marks
A student studies the equipotential surfaces around an isolated, uniform planet and considers the work done when a small mass is moved between points in the field.
Explain why no work is done on a small mass when it is moved along an equipotential surface.2 marks
Between distances r = 7.0 × 10⁶ m and r = 9.0 × 10⁶ m from the centre of the Earth, a graph of gravitational field strength g against r is approximately a straight line, falling from 8.1 N kg⁻¹ to 4.9 N kg⁻¹. The Earth has mass 5.97 × 10²⁴ kg.
Use the graph information to estimate the change in gravitational potential between these two distances.3 marks

Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).