Inattentive Driver A 1200 kg car moving at 5.1 m/s is initially traveling north
ID: 1988116 • Letter: I
Question
Inattentive Driver A 1200 kg car moving at 5.1 m/s is initially traveling north in the positive y direction. After completing a 90° right-hand turn to the positive x direction in 4.6 s, the inattentive operator drives into a tree, which stops the car in 360 ms.(a) In unit-vector notation, what is the impulse on the car during the turn?
N·s i + N·s j
(b) In unit-vector notation, what is the impulse on the car during the collision?
N·s i + N·s j
(c) What is the average force that acts on the car during the turn?
N i + N j
(d) What is the average force that acts on the car during the collision?
N i + N j
(e) What is the angle between the average force in (c) and the positive x direction?
°
Explanation / Answer
Initial momentum ( before the turn) = 1200 *5.1 j N-s
Final momentum = 1200 * 5.1 i N-s
a)
Hence impulse during the turn = Change in momentum = 6120 ( i - j ) N-s
After the collision, Final momentum = 0
b)
Hence Impulse during collision = 0 - 6120 i = -6120 i Ns
c)
Average force during the turn = Impluse/time = 6120/4.6 ( i - j ) N = 1330.43 ( i - j ) N
d)
Average force during the collision = -6120/0.36 i = - 17000 i N
e)
Angle between the average force in c and x axis be
tan = -1/1 = -1
=> = -45 degrees