# Force and Motion

1. Feb 10, 2005

### Kp0684

A car traveling at 53km/h hits a bridge abutment. A passenger in the car moves forward a distance of 65cm (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 41kg? ............. i get 14.7m/s2 for the cars speed which is my (a), and my mass is 41kg.....F=ma gives me 602Newtons...........i am lost on which equation to use....need help.....

2. Feb 11, 2005

### Davorak

I would use one of the kinematic equations to find the acceleration and then multiple that by the mass of the torso myself.

Edit:Should probably post questions like these in the homework section.

Last edited: Feb 11, 2005
3. Feb 11, 2005

### Staff: Mentor

14.7m/s is the car's initial speed, not acceleration. To find the acceleration, follow Davorak's advice. (Hint: Find a kinematics equation that relates acceleration, distance, and speed.)

(I am moving this to the Homework forum, where it belongs.)

4. Feb 11, 2005

### xanthym

However, it's also true the original kinetic energy E=(1/2)(41 kg)(14.7 m/s)^2 was dissipated to 0 over 0.65 meters by the assumed constant force F=(E/0.65).

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Last edited: Feb 11, 2005
5. Feb 12, 2005

### Kp0684

i have the magnitude force equal to (6.82 x 10^3 N).........

6. Feb 12, 2005