Q252 · Practice questionSimple familiar4 marks
QUESTION 252 (4 marks)
The diagram shows a spherical planet and a satellite at P in a circular orbit. The planet has radius ; P is at radius from its centre. Ignore other gravitational fields.
a)[2 marks]
Sketch four gravitational field lines outside the planet, with arrows. At P, add an arrow for the satellite extquotesingle s acceleration.
b)[2 marks]
An astronaut says gravity is zero at P because the satellite feels weightless. Assess this claim using the ratio of field strength at P to surface field strength.
WORKED SOLUTION
4 marksPractice marking scheme
ANSWER
(a) Radial inward field lines; acceleration at P points toward the planet centre. (b) ; weightlessness is not zero gravity.
Worked solution
(a) Gravitational field direction is the force direction on a small test mass. Gravity provides the inward acceleration of the freely orbiting satellite.
(b) , so . Astronaut and craft are both in free fall; absence of a support force produces apparent weightlessness.
Equivalent physically justified methods, alternative valid sketches and consistent units accepted.
Accept sensible significant figures and consistent rounding from stated constants.
Part a: Draw radial field lines with inward arrowheads.
Part a: Draw the acceleration at P inward toward the centre.
Part b: Calculate the nonzero field-strength ratio.
Part b: Explain apparent weightlessness through common free fall or absence of a support force.
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