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Gravitational fields
This A-level only topic extends mechanics to gravitational interactions.
0
Objectives
10
Flashcards
10
Questions
90 min
Study time
AqaA LevelPhysicsFields and their consequences
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Syllabus checklist
What you need to know
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Newton's law of gravitation4 objectives
- State and apply Newton's law of gravitation.
- Explain inverse-square behaviour in gravitational force.
- Calculate gravitational forces between masses.
- Distinguish gravitational force from gravitational field strength.
Gravitational field strength4 objectives
- Define gravitational field strength as force per unit mass.
- Calculate gravitational field strength around spherical masses.
- Link gravitational field strength to weight.
- Interpret gravitational field strength graphs.
Gravitational potential4 objectives
- Define gravitational potential in a field.
- Calculate changes in gravitational potential energy.
- Interpret gravitational potential graphs.
- Link potential difference to work done in moving masses.
Orbits of planets and satellites4 objectives
- Explain circular orbits using gravitational force as centripetal force.
- Calculate orbital speed and period for simple circular orbits.
- Explain geostationary orbit conditions.
- Link orbital radius to speed, period and field strength.
Key terms
Newton's law of gravitationgravitational field strengthInverse-square lawGravitational ForceGravitational Field StrengthWeightGravitational Potential Energyweightgravitational field strength graphinverse-square lawgravitational potentialgravitational potential energy
Exam tips
- Understanding Newton's Law of Gravitation: Remember that the gravitational force between two masses is calculated using the formula F = G * (m1 * m2) / r^2, where F is the gravitational force, G is the gravitational constant, m1 and m2 are the masses, and r is the distance between their centers.
- Understanding Inverse-Square Law: Remember that gravitational force decreases with the square of the distance between two masses. Use the formula F = G * (m1 * m2) / r^2 to calculate the gravitational force.
Common mistakes
- Misunderstanding Gravitational Force Calculation: To calculate gravitational force, use Newton's law of gravitation: F = G * (m1 * m2) / r^2. Substitute the correct values for masses and the distance between their centers. For example, if m1 = 5 kg, m2 = 10 kg, and r = 2 m, then F = 6.674 × 10^-11 * (5 * 10) / (2^2) = 8.3425 × 10^-11 N.
- Misunderstanding Inverse-Square Law: To fix this, remember that the gravitational force (F) between two masses (m1 and m2) is given by the formula F = G * (m1 * m2) / r^2. When the distance (r) is doubled, substitute into the formula: F = G * (m1 * m2) / (2r)^2 = G * (m1 * m2) / (4r^2), showing that the force is reduced to a quarter.
Practice preview
- What does Newton's law of gravitation state?
- How does the gravitational force change if the distance between two masses is doubled? Scenario focus: orbital motion in a distinct A-Level Physics fields context; identify the field quantity, source, direction, and unit before selecting the answer.
- If the mass of one object is tripled, how does the gravitational force between it and another object change?
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