Multiple choice

An automobile travelling with a speed of $60$ kmph, can apply brakes to stop within a distance of $20$ m. If the car is going twice as fast, the stopping distance will be

  1. $20$ m
  2. $40$ m
  3. $60$ m
  4. $80$ m
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D Correct answer
Explanation

Stopping distance is proportional to the square of the velocity (d proportional to v^2). If the speed doubles, the stopping distance increases by a factor of 2^2 = 4. Therefore, 20 m * 4 = 80 m.

AI explanation

Stopping distance is directly proportional to the square of the velocity when the retardation is constant. The new speed is twice the original speed (120 kmph is twice 60 kmph), so the stopping distance increases by a factor of 2 squared, which is 4. Multiplying the original distance of 20 m by 4 gives a new stopping distance of 80 m.

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