Define gravitational potential , φ .

The work done per unit mass in bringing a small test mass from infinity to that point.

Why does gravitational potential always have a negative value?

It is defined as zero at infinity , and since the gravitational force is attractive , work must be done on a mass to move it away from the mass to infinity, so the potential at any closer point is lower than zero.

How does gravitational potential change with distance from a mass?

It increases (becomes less negative) as distance from the mass increases.

A LevelPhysicsCambridge (CIE)Flashcards13. Gravitational FieldsGravitational Potential

Gravitational Potential (Cambridge (CIE) A Level Physics): Flashcards

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FrontGravitational Potential
Define gravitational potential, φ.

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Cards in this collection (8)

Define gravitational potential, φ.
The work done per unit mass in bringing a small test mass from infinity to that point.
Why does gravitational potential always have a negative value?
It is defined as zero at infinity, and since the gravitational force is attractive, work must be done on a mass to move it away from the mass to infinity, so the potential at any closer point is lower than zero.
How does gravitational potential change with distance from a mass?
It increases (becomes less negative) as distance from the mass increases.
State the equation for gravitational potential φ due to a point mass M at distance r, and define each symbol.
$ϕ = - \frac{G M}{r}$
- φ = gravitational potential (J kg^-1)
- G = Newton's gravitational constant
- M = mass of the body producing the field (kg)
- r = distance from the centre of the mass to the point (m)
The gravitational potential difference between two points is given by $Δ ϕ = ϕ_{f} - ϕ_{i}$ , where $ϕ_{f}$ is the .......... gravitational potential.
The gravitational potential difference between two points is given by $Δ ϕ = ϕ_{f} - ϕ_{i}$ , where $ϕ_{f}$ is the final gravitational potential.
Define the gravitational potential energy of a system of two point masses, and state the equation.
The work done to assemble the system from infinite separation of its components: $E_{p} = - \frac{G m_{1} m_{2}}{r}$
State the equation relating the work done, W, to move a mass m in a gravitational field to the change in gravitational potential, ΔV.
$W = m Δ V$
True or False?
The equation ΔG.P.E. = mgΔh can be used to find the change in gravitational potential energy of a satellite moving between two orbits far above the Earth's surface.
False.
mgΔh only applies in a uniform gravitational field near the Earth's surface. Far from the surface, g is not constant, so $Δ E_{p} = G m_{1} m_{2} (\frac{1}{r_{1}} - \frac{1}{r_{2}})$ must be used instead.

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