In: Physics

# What is the average retarding force on the vehicle?

The driver of a three-wheeler moving at 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.

## Solutions

##### Expert Solution

Given,

Initial velocity, $$u= 36 km/h$$

Final velocity, $$v = 0$$

Mass of the three-wheeler, $$m_1= 400 Kg$$

Mass of the driver, $$m_2 = 65 Kg$$

Time taken to bring the vehicle to rest = 4.0 s

$$Acceleration,\ a = v- u/t = (0 – 10)/ 4 =\ – 2.5 m/s$$

$$Now,\ F = (m1 + m2)/ a = (400 + 65) \times (-2.5)$$

$$=\ – 1162.5 N =\ – 1.16 \times 10^3 N.$$

The negative sign shows that the force is retarding.

The average retarding force on the vehicle is $$– 1.16 \times 10^3 N.$$