
Concept explainers
(a)
The minimum possible distance the person can be away from the light when the light turns yellow.
(a)

Answer to Problem 39P
The distance needed by the car to stop safely is
Explanation of Solution
Given:
The reaction time of the driver is
The initial speed of the car is
The maximum possible rate of deceleration is
Formula Used:
The expression for the distance travelled by the car is given by,
The distance travelled by the car for the reaction time
Calculation:
The car comes to complete stop after reaching the light thus the value of the final velocity is
The distance travelled by the car is calculated as,
The distance travelled by the car for the reaction time
The total distance travelled by the car is calculated as,
Conclusion:
Therefore, the distance needed by the car to stop safely is
(b)
The maximum distance that must be between the light and the car so that the car must pass the light before the light turns red.
(b)

Answer to Problem 39P
The distance up to which the car must be away from light, to make it through the light is
Explanation of Solution
Given:
The maximum rate of acceleration after the brakes are applied is
The initial speed of the car is
Formula Used:
The reaction time after the light turns red is
The expression for the distance traveled by the car is given by,
The expression for the total distance required to travel to make it through the light is given by,
Calculation:
The distance traveled by the car is calculated as,
The total distance required to travel to make it through the light is calculated as,
Conclusion:
Therefore, the distance up to which the car must be away from light, to make it through the light is
(c)
The minimum possible distance the person can be away from the light when the light turns yellow.
(c)

Answer to Problem 39P
The distance needed by the car to stop safely is
Explanation of Solution
Given:
The reaction time of the driver is
The initial speed of the car is
The maximum possible rate of deceleration is
The maximum rate of acceleration after the brakes are applied is
Formula Used:
The expression for the distance travelled by the car is given by,
The distance travelled by the car for the reaction time
The reaction time after the light turns red is
The expression for the distance traveled by the car is given by,
The expression for the total distance required to travel to make it through the light is given by,
Calculation:
The car comes to complete stop after reaching the light thus the value of the final velocity is
The distance travelled by the car is calculated as,
The distance travelled by the car for the reaction time
The total distance travelled by the car is calculated as,
The distance traveled by the car is calculated as,
The total distance required to travel to make it through the light is calculated as,
Conclusion:
Therefore, the distance needed by the car to stop safely is
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Chapter 2 Solutions
Physics Fundamentals
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