MYP Physics · 15 · structured
Gravitational field above Earth
Fields and gravity · Original GioPhysics question with a detailed, mark-by-mark answer guide.
- Demand
- routine
- Marks
- 6
- Topics
- 2
- Answer
- Complete
At Earth's surface the gravitational field strength is 9.8 N kg⁻¹. A 500 kg satellite is at a distance of two Earth radii from Earth's centre. Treat Earth as a sphere and use the inverse-square relationship.
- a
Calculate Calculate the gravitational field strength at the satellite.
3 marks - b
Calculate Calculate the gravitational force on the satellite.
2 marks - c
Explain Explain why the satellite is not weightless at this position.
1 mark
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a
Calculate Calculate the gravitational field strength at the satellite.
List the given quantities with units, identify the required quantity, write the governing relationship before substituting, and keep extra digits until the final line so rounding does not distort the result.
- 1
Recognises that doubling distance from the centre reduces field strength by 2² = 4.
- 2
Calculates 9.8 ÷ 4.
- 3
Obtains 2.45 N kg⁻¹.
b
Calculate Calculate the gravitational force on the satellite.
List the given quantities with units, identify the required quantity, write the governing relationship before substituting, and keep extra digits until the final line so rounding does not distort the result.
- 1
Uses F = mg or F = mass × field strength.
- 2
Obtains F = 500 × 2.45 = 1225 N, towards Earth's centre.
c
Explain Explain why the satellite is not weightless at this position.
State the outcome first, then link cause to effect with the relevant physical principle. Each link in the reasoning should be explicit enough to earn its own marking point.
- 1
Gravity is still acting; apparent weightlessness in orbit is due to continuous free fall, not zero gravitational field.
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