Force and Motion

  • Thread starter Kp0684
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  • #1
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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.....
 

Answers and Replies

  • #2
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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:
  • #3
Doc Al
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Kp0684 said:
i get 14.7m/s2 for the cars speed which is my (a),
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
xanthym
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Kp0684 said:
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.....
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).

~~
 
Last edited:
  • #5
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i have the magnitude force equal to (6.82 x 10^3 N).........
 
  • #6
xanthym
Science Advisor
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Your answer F=(6.82x10^3 N) is CORRECT.
 

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