Suspended particles in muddy water are larger and heavier, so they settle at the bottom with time. Milk contains much smaller colloidal particles that remain uniformly dispersed and do not settle easily when left undisturbed.
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The minute hand completes 1.5 revolutions in 90 minutes. Distance = 1.5 × 2π × 7 = 21π cm. Displacement = 14 cm. Average speed = 21π/5400 cm s⁻¹ and average velocity = 14/5400 cm s⁻¹ downward.
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.
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.