O-LevelPhysicsForces5054/21 · Oct/Nov 2025 · Q910 Marks

An object moves through space. It is a large distance from any other object.

(a)There are no external forces acting on the object. Describe two features of the motion of the object that are a consequence of Newton's first law.[2]
(b)(i)State why a force must act on Venus to keep it following an approximately circular orbit.[1]
(b)(ii)State what causes this force, and state the direction of the force.[3]
(b)(iii)The average radius of the orbit of Venus is 1.1 × 10¹¹ m. It takes Venus 5400 hours to complete one orbit of the Sun. Calculate the average orbital speed of Venus around the Sun.[2]
(b)(iv)Planet X is closer to the Sun than Venus. State the name of planet X and state how its orbital speed around the Sun compares with the orbital speed of Venus.[2]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2025). The mark or mark type is shown in brackets.

[B1] speed is constant
[B1] (motion is) in a straight line
[B1] to change the direction of the motion/velocity (of Venus) / otherwise it would move in a straight line
[B1] gravitational field/gravitational attraction/gravity
[B1] (gravitational field) of Sun
[B1] towards centre of circle/Sun/inward
[C1] (speed =) 2πr / T or (2 × π) × 1.1 × 10¹¹ / (5400 × (3600))
[A1] 3.6 × 10⁴ (m/s)
[B1] Mercury
[B1] (its speed is) greater (than that of Venus)

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