Question

An air bag increase impact time to reduce force experienced by a driver of a car during collision. A bus hits a car that is parked on the road from behind. The car accelerates to 4.5 m/s in 0.15 s . what force does the driver of the car experience if he is not wearing the seatbelt during the accident . Assume that the combine mass of the car and the driver is 2580 kg . if the car has an air bag that increased the impact time to 0.450 s, what force was experience by the driver ?

Answer 1

First, write the equation for acceleration:

$$a=\frac vt.$$

Find force by Newton's second law:

$$F=ma=m\frac vt.$$

Without the airbag, the force will be

$$F_1=2850\frac {4.5}{0.15}=85500\text{ N}.\\\space\\ F_2=2850\frac {4.5}{0.45}=28500\text{ N}$$

with the airbag. We see that the airbag reduces the force thrice.