Q5.8 The driver of a three-wheeler moving with a speed of 36 km/h sees a child standing in the middle of the road and brings his vehicle to rest in 4.0 s just in time to save the child. What is the average retarding force on the vehicle? The mass of the three-wheeler is 400 kg and the mass of the driver is 65 kg.
Total mass of the system = 400 + 65 = 425 kg
Using first law of motion, we get
Since the car comes to rest, thus final velocity will be zero.
or
So the force required :
or
or
So the magnitude of the force is 1162.5 N and it is retarding force.