For A, acceleration = 1 m s⁻² and displacement in 5 s = 12.5 m. For B, acceleration = 0.3 m s⁻² and displacement in 10 s = 15 m. Their velocity-time graphs are straight lines from the origin.
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For the first 120 s, displacement = 6 × 120 = 720 m. During the next 6 s, displacement = 6 × 6 + ½ × 1 × 6² = 54 m. Total displacement = 774 m.
The distance travelled is approximately equal to the area under the velocity-time graph. Estimating the areas of the trapeziums from the graph gives a total distance of approximately 45 km.
For constant velocity, the area from 20–100 s is a rectangle: 3 × 80 = 240 m. For decreasing velocity, area from 100–120 s = ½(3+2)×20 = 50 m. Total displacement = 320 m; average acceleration = (2−0)/120 = 0.0167 ...
An object kept on the Earth can be considered at rest relative to the Earth, because its position does not change with respect to the Earth. However, relative to the Sun, it is moving.