In a crash test, a truck with mass 2300 kg traveling at 25 m/s smashes head-on i
ID: 1525547 • Letter: I
Question
In a crash test, a truck with mass 2300 kg traveling at 25 m/s smashes head-on into a concrete wall without rebounding. The front end crumples so much that the truck is 0.66 m shorter than before.
A. What is the average speed of the truck during the collision (that is, during the interval between first contact with the wall and coming to a stop)? vavg = _______ m/s
C. What is the magnitude of the average force exerted by the wall on the truck during the collision?
D. It is interesting to compare this force to the weight of the truck. Calculate the ratio of the force of the wall to the gravitational force on the truck. This large ratio shows why a collision is so damaging.
AtExplanation / Answer
(A) V<avg> = (25 + 0) / 2 = 12.5 m/s
(B) vf^2 - vi^2 = 2 a d
0^2 - 25^2 = 2 a (0.66)
a = - 473.48 m/s^2
vf = vi + a t
0 = 25 - 473.48 t
t = 0.0528 sec
(c) F = m a = 2300 x 473.48
F = 1089015 N
(D) Favg / mg = (1089015) / (2300 x 9.8)
= 48.3