Two objects move on a horizontal frictionless surface along the same line in the same
direction which we shall refer to as the forward direction. The trailing object of mass
2.0 kg has a velocity of 15 m/s forward. The leading object of mass 3.2 kg has a
velocity of 11 m/s forward. The trailing object catches up with the leading object and the
two objects experience a completely inelastic collision. What is the final velocity of each
of the two objects?
BEFORE
AFTER
m
v
m
= 15
v = 11
v ′
1
2
s
1
s
2
1
2
m = 2.0 kg
m = 3.2 kg
1
2
Σp = Σ ′
→
→
p
p + p = ′
p
1
2
12
mv + m v = (m + m )v ′
1 1
2 2
1
2
mv + m v
1 1
2
2
v ′ = m +m
1
2
2.0 kg 15
(
m / s) + 3 2
. kg 11
(
m / s)
v ′ =
2.0 kg + 3 2
. kg
m
v ′ =12 54
.
s
m
v ′ =13 s
m
The final velocity of each of the objects is 13
forward.
s
23