No, Ravi’s mother probably will not know what happened. Grandpa deliberately told her that he had a quiet morning, while Ravi remained confused and embarrassed. Ravi also chose not to reveal the truth.
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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.