Orbital speeds of planets and satellites
3 marks · EasyThe table shows some information about two planets:
| Planet | Mass (Earth=1) | Radius (Earth=1) |
|---|---|---|
| Planet A | 1.5 | 1.0 |
| Planet B | 1.0 | 2.0 |
Which planet has the higher gravitational field strength at its surface? Explain your answer.
Which planet would an object weigh less on? Give a reason.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) Planet A has the higher gravitational field strength because it has greater mass and the same radius as Earth. Planet B has same mass but double the radius, which decreases gravitational field strength.
(b) Planet B, because weight is less where gravitational field strength is lower.
Show mark scheme and worked solution
Marking points
M1 (a) · 1 mark · Correctly selects Planet A as having greater field strength.
B1 (a) · 1 mark · Explains that greater mass and/or smaller radius increase field strength, referencing values in table.
B2 (b) · 1 mark · Correctly identifies Planet B and gives a valid reason (lower field strength means lower weight).
Worked solution
a) Planet A has higher field strength because it has greater mass (1.5 times Earth) and the same radius, increasing g. Planet B has the same mass as Earth but twice the radius, making g lower. b) Objects weigh less on Planet B, as the gravitational field strength is lower due to the larger radius.