A passenger car traveling in a straight line collides head-on with a stationary barrier
PHYSICS · Multi-part · CBSE · Physics · Laws of Motion · Laws of Motion
Problem
A 1300kg passenger car traveling 22ms−1 in a straight line collides head-on with a stationary barrier. Engineers test two different barrier designs:
• Barrier X is a rigid concrete wall that brings the car to rest in 45ms.
• Barrier Y is an energy-absorbing structure that brings the car to rest in 120ms.
Assume that the horizontal net force exerted by each barrier on the car is approximately constant during each impact and that the car’s mass remains constant. Neglect all other horizontal forces.
Answer the following questions qualitatively or with symbolic reasoning; no numerical calculation of force magnitudes is required.
(a) Describe, in words, how the magnitude of the average horizontal force exerted on an object during a collision is related to the object’s change in momentum and the time interval of the collision.
(b) Using your reasoning from part (a), compare the magnitudes of the average horizontal forces exerted on the car by Barrier X and Barrier Y. Express the force exerted by Barrier Y as a factor of the force exerted by Barrier X and justify your answer.
(c) Explain how the difference in average force between the two barriers is likely to influence the severity of injuries experienced by the car’s occupants. In your explanation, make explicit reference to Newton’s second law and the stresses experienced by the human body.