The front 1.20 m of a 1,300-kg car is designed as a \"crumple zone\" that collap

ID: 1373020 • Letter: T

Question

The front 1.20 m of a 1,300-kg car is designed as a "crumple zone" that collapses to absorb the shock of a collision.

(a) If a car traveling 29.0 m/s stops uniformly in 1.20 m, how long does the collision last?

(b) What is the magnitude of the average force on the car?

(c) What is the magnitude of the acceleration of the car? Express the acceleration as a multiple of the acceleration of gravity.

Note: I've already found the correct answer to part (a): t = 0.0828 s

Note: For (b), I got the answer 3.93 x 10^5 N, but it says it is incorrect.

a. thirdequation of motion is

v2 = u2+ 2 * a * s

v = finalvelocity = 0, u = initialvelocity = 29 m/s,a = acceleration

s = distance = 1.2m

0 = 292+ 2 * a * 1.2

a = - 841/ 2.4 = - 350.416 m/s2

( - ve sign indicatesretardation.)

first equationis

v = u+ a* t

0 = 29+ ( - 350.416) * t

t = 29/ 350.416 = 0.08275 s

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