_{Up Learn – A Level physics (AQA) – GRAVITATIONAL FORCE AND FIELD}

_{Up Learn – A Level physics (AQA) – GRAVITATIONAL FORCE AND FIELD}

**Combining Gravitational Fields**

**Combining Gravitational Fields****Resultant gravitational field strength is the vector sum of individual gravitational field strengths.**

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### More videos on Gravitational Force and Field:

^{Introduction to Gravitational Fields (free trial)}

^{Gravitational Field Strength}

^{Test Masses (free trial)}

^{Calculating Gravitational Field Strength (free trial)}

^{Gravitational Field around the Earth (free trial)}

^{Gravitational Vector Fields (free trial)}

^{Comparing Gravitational Fields (free trial)}

^{Combining Gravitational Fields}

^{Calculating Combined Gravitational Fields}

^{Finding Points with No Gravitation Field (free trial)}

## Gravitational Force and Field

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2. Reminder About Gravity

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3. Factors that Affect Gravitational Force 1 – Mass

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4. Factors that Affect Gravitational Force 1 – Distance

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5. Article – Distances Between Masses

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6. Point Masses

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7. Newton’s Equation for Gravity

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2. Gravitational Field Strength

3. Test Masses

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4. Calculating Gravitational Field Strength

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5. Gravitational Field around the Earth

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6. Gravitational Vector Fields

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7. Gravitational Field Lines

8. Comparing Gravitational Fields

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9. Combining Gravitational Fields

10. Calculating Combined Gravitational Fields

11. Finding Points with No Gravitation Field

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12. Graphs of Gravitational Field

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2. Changes in Gravitational Potential Energy in a Uniform Field

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3. Gravitational Potential Energy – Work Done

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4. Gravitational Potential Energy at Infinity

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5. Absolute Gravitational Potential Energy

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6. Combining Gravitational Potential Energies

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7. Moving a Mass in a Gravitational Field

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8. Two Equations for GPE

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9. Deriving Two Equations for Ep – Article

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10. Escape Velocity

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2. The Gravitational Potential

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3. Values of Gravitational Potential

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4. Gravitational Potential Difference

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5. Work Done and Potential Difference

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6. Equipotentials Surface Around a Point Mass

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7. Equipotentials and Field Lines

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8. Work Done Along Equipotentials

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9. Finding Gradients of Tangents (Recap) – Article

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10. Potential Graphs and Potential Gradient

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11. Gravitational Fiend Strength and Graphs of Gravitational Potential

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12. Finding Areas Under Curves – Article

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13. Gravitational Potential and Graphs of Gravitational Field Strength

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14. Worked Example – Finding Potential Difference from a Field Strength Graph – Article

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15. Equipotentials and Potential Gradient

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16. Combining Potentials

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17. Combining Potential Graphs

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2. Recap of Circular Motion – Article

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3. Kepler’s Third Law

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4. Proving Kepler’s Third Law

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5. Recap of Log Laws – Article

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6. Graphing Kepler’s Third Law

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7. Graphing Kepler’s Third Law – Article

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8. What are Satellites?

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9. Geostationary Satellites

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10. Polar and Geosynchronous Orbits – Article

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11. Energy of Orbiting Satellites

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12. Escape Velocity for Satellites

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So far, we’ve talked about the effects of a single gravitational field on a small mass in the field.

But in reality, there are lots of large masses around…… like stars…… planets…… and moons …… and all their gravitational fields overlap!

For instance, here are two stars.

At this point the gravitational field from *this* star points in *this *direction…

… and the gravitational field from *this* star points in *this *direction.

The gravitational fields of the two stars are pulling in different directions.

So the overall gravitational field at this point is the vector sum of the two.

Next, at *this* point…

… the gravitational fields both point in *this* direction

So the overall gravitational field is in this direction…

… and it’s stronger than the individual gravitational fields at that point.

Whereas at *this* point, the gravitational fields point in exactly opposite directions

… so the fields partly cancel out and the overall gravitational field strength is weaker.

And at *this* point, the individual fields completely cancel each other out, so the overall gravitational field strength is zero!

So, how do we calculate the overall gravitational field strength?

We’re going to look at that next.

But to sum up for now…

When a point is in two gravitational fields, the gravitational field strengths combine.

The direction *and* the magnitude of the individual gravitational fields combine, so we add the gravitational field strengths as…

The direction *and* the magnitude of the individual gravitational fields combine, so we add the gravitational field strengths as vectors.