Gravitational Potential & Potential Energy — A/L Physics

What must I remember about Gravitational Potential & Potential Energy?

• Gravitational Potential (V): Work done by an external agent in bringing a unit mass from infinity to that point without acceleration: V = - (G M) / r (scalar quantity, units J/kg).
• Gravitational Potential Energy (U): Work done in assembling masses from infinite separation to distance r: U = m V = - (G M m) / r (J); always negative for bound states.
• Relationship between Field and Potential: Field strength is the negative spatial gradient of potential: g = - dV/dr; potential difference ΔV = - ∫ g · dr.
• Equipotential Surfaces: Surfaces on which gravitational potential is everywhere constant; field lines are everywhere PERPENDICULAR to equipotential surfaces; zero work done in moving a mass along an equipotential surface.

Test yourself (1 minute)

1. Reference Point at Infinity

   Gravitational potential is conventionally zero at infinity (V_∞ = 0); because gravity is attractive, potential everywhere in real space is strictly NEGATIVE.

2. Potential difference near Earth's surface

   For small height change h << R: ΔU = U(R+h) - U(R) = -GMm/(R+h) - (-GMm/R) ≈ (GMm/R²)*h = mgh.

3. Energy Conservation in gravitational fields

   (1/2)m v1² - (GMm / r1) = (1/2)m v2² - (GMm / r2).

Practise Gravitational Potential & Potential Energy questions today

Source: NIE G.C.E. (A/L) Physics Resource Book - Unit 5: Gravitational Fields

What should I study first?

What comes next?

Next in the syllabus

Where does Gravitational Potential & Potential Energy fit in the syllabus?

Unit 5.3 · Year 1 · Term 3