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CAIE IGCSE Physics Newton's First Law

Practise linking zero resultant force to rest or constant straight-line velocity and explaining balanced forces, inertia and safety-belt scenarios.

Syllabus
2026–2028
Course
Physics 0625

Exam points

  • conclude that zero resultant force gives rest or constant speed in a straight line
  • balance driving force against drag, or weight against support, when velocity is constant
  • apply inertia to explain why an unrestrained passenger continues forwards during a sudden stop

1.5.1.4—An object either remains at rest or question 1

[Maximum number: 2]

Fig. 1.1 shows a straight section of a river where the water is flowing from right to left at a speed of 0.54 m/s0.54 \mathrm{~m} / \mathrm{s}.

Fig. 1.1 (not to scale)

Fig. 1.1 (not to scale)

A swimmer starts at point P and swims at a constant speed of 0.72 m/s0.72 \mathrm{~m} / \mathrm{s} relative to the water and at right angles to the current.

When the swimmer is crossing the river, his actions produce a constant forward force on his body.

Explain why he moves at a constant speed.
[Total: 9]

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