Question

A car traveling at 69 km/h hits a bridge abutment. A passenger in the car moves forward a distance of 65 cm (with respect to the road) while being brought to rest by an inflated air bag. What magnitude of force (assumed constant) acts on the passenger's upper torso, which has a mass of 47 kg?

Answer 1

`F=(1)/(2d)mv^2=1/(2*0.65)*47*(19.2)^2=13328N`

Step-by-step explanation:

`v=69km/h*(1000m/1km)*(1h/3600s)=19.2m/s`

In order to solve this problem we use the Energy-Work principle. The change in total energy is equal to the work done on the system:

`E_(final)-E_(initial)=Work`

the initial energy is only kinetics, the final energy is zero, and the work is negative and made by the constant force of the airbag:

`0-(1)/(2)mv^2=-F*d`

`F=(1)/(2d)mv^2=1/(2*0.65)*47*(19.2)^2=13328N`