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

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

**Gravitational Field Strength**

**Gravitational Field Strength****What do we mean by gravitational field strength?**

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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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We’ve seen that all masses experience a gravitational force towards all other masses.

The magnitude of the gravitational force is given by this equation.

And the direction of that force is always towards the other mass.

Now, another way of understanding gravity is to say that all masses have a gravitational field around them…

Which, as we saw in the Introduction to Fields, is…

A gravitational field is a region where any mass experiences a non-contact force.

For a spherical mass like the Earth, we’ve already seen that the gravitational field lines look like this.

And the closer together the lines are at a particular point, the stronger the field is at that point.

But what do we mean by “field strength” or “the strength of the field”?

Well, gravitational field strength is defined as gravitational force per unit mass, at a specific point in a gravitational field.

And it’s a vector…

The direction of the gravitational field strength vector is the same as the direction of the gravitational force vector. They both point towards the source mass.

So, if we take a mass like a satellite and move it to a point with higher gravitational field strength…we know that the gravitational force that the satellite experiences will increase.

And what if we replace the satellite with a more massive object, like an asteroid?

Well, we know that the asteroid will experience…

If we replace the satellite with a more massive object, like an asteroid, we know that the asteroid will experience a larger gravitational force than the satellite.

However, field strength is force per unit mass, so the field strength doesn’t change!

The gravitational field strength around a mass like a planet depends on the planet’s mass…

But not on the mass of the object that’s in the gravitational field.

So, in summary…

All masses are surrounded by a region where other masses experience a non-contact force.

This region is called a…

This region is called a gravitational field.

And the gravitational field strength is defined as the…

The gravitational field strength is defined as the gravitational force per unit mass that a mass would experience in a gravitational field.