SAMPLE PROBLEM 13.13
K
A 20-Mg railroad car moving at a speed of 0.5 m/s to the right collides with a
$ 35-Mg car which is at rest. If after the collision the 35-Mg car is observed to
move to the right at a speed of 0.3 m/s, determine the coefficient of restitution
between the two cars.
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SAMPLE PROBLEM 13.13
A 20-Mg railroad car moving at a speed of 0.5 m/s to the right collides with a
35-Mg car which is at rest. If after the collision the 35-Mg car is observed to
move to the right at a speed of 0.3 m/s, determine the coefficient of restitution
between the two cars.
Solution.
served.
v.
20 Mg
=0.5
We express that the total momentum of the two cars is con¬
m/s
35 Mg
vb=°
VA
v'.=0.3m/s
20 Mg
35 Mg
mAVA + mBVB = mAVA + mBVB
(20 Mg)( +0.5 m/s) + (35 Mg)(0) = (20 Mg)v'A + (35 Mg)(+0.3 m/s)
v'A = -0.025 m/s v'A = 0.025 m/s «The coefficient of restitution is obtained by writing
MB
v'b-v'a _ +0-3 ~ (-0-025) _ 0.325
va ~ vb ~~
+0-5 - °
~ 0.5
e = 0.65