- #1
Kaon
- 2
- 0
Homework Statement
The front of a 1400 kg car is designed to absorb the shock of a collision by having a "crumple zone" in which the front 1.20 m of the car collapses in absorbing the shock of a collision.
(a) If a car traveling 25.0 m/s stops uniformly in 1.20 m, how long does the collision last?
answer in s
NOTE: I know this is not part of the template, but I needed to put it in somewhere. I realize this problem can be easily solved using kinematics equations and constant acceleration, but I'm trying to figure out why using the impulse doesn't work. See attempt section for more.
Homework Equations
vf = vi + at
vf2 = vi2 + 2ax
I= m[tex]\Delta[/tex]v
I= m(vf) - m(vi)
The Attempt at a Solution
CORRECT ANSWER:
0= 25 + at
0= 252 + 2ax
a = -252/2ax = -260.4 m/s2
t = -25/a = 0.096 s
TRIAL USING IMPULSE:
I = 0 - m(25) = -35 000
I = m[tex]\Delta[/tex]x/[tex]\Delta[/tex]t *I realize this may be where the problem lies
1.2m/-35 000 = t
t = 0.048 s *I also notice that this is exactly 1/2 of the right answer