Example 1 · level 1
A stone rolls down a slope starting from rest with acceleration 2 m/s². What is its velocity after 3 s (in m/s)?
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- v = 0 + 2 × 3 = 6 m/s.
Answer: 6
CLASS 9 SCIENCE · MOTION
Equations of motion
For uniform acceleration: v = u + at, s = ut + ½at², v² = u² + 2as. List u, v, a, t, s and pick the equation with one unknown.
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Worked examples
Example 2 · level 2
A train moving at 5 m/s accelerates uniformly at 6 m/s² for 5 s. Find the distance it covers in this time (in m).
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- s = 5 × 5 + ½ × 6 × 5²
- = 25 + 75 = 100 m.
Answer: 100 m
Example 3 · level 3
A car moving at 30 m/s applies brakes giving a uniform retardation of 5 m/s². How far (in m) does it travel before stopping?
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- 0 = 900 − 10s
- s = 900 ÷ 10 = 90 m.
Answer: 90 m