Question
Driver of a car is driving at the speed 9-8 m/s. He saw a child standing in the middle of road and applied the brakes when the car was at a distance 4.9m away from the child. Show that the minimum retarding force of the brakes on the car to just save the child must be half the weight of the car.
Solution
The car must stop by travelling the maximum distance of 4.9m, in order to save the child.
Let M be mass of the car.
Here,
Initial velocity of the car, u = 9.8 m/s
Final velocity, v = 0
MAximum distance travelled,
Therefore minimum retardation of the car is,
The minimum retarding force on the car is,
Now,
Thus,
Retarding force =
Let M be mass of the car.
Here,
Initial velocity of the car, u = 9.8 m/s
Final velocity, v = 0
MAximum distance travelled,
Therefore minimum retardation of the car is,
The minimum retarding force on the car is,
Now,
Thus,
Retarding force =
