vf
m1v1
m2v2
m1
m2
vf
m1v1
m2v2
m1
m2
vf
(2300 lbm)(29 ft/sec)
(2800 lbm)(11 ft/sec)
2300lbm
2800 lbm
vf
19.1 ft/sec
Force and Motion
MOMENTUM PRINCIPLES
Rev. 0
Page 9
CP-03
If the initial velocities of the two objects (v and v ) are known, then the final velocity (v ) can
1
2
f
be calculated by rearranging Equation 3-10 into Equation 3-11.
(3-11)
Example:
Consider that the railroad cars in Figure 1 have masses of m = 2300 lbm and
1
m = 2800 lbm. The first car (m ) is moving at a velocity of 29 ft/sec and the second car
2
1
(m ) is moving at a velocity of 11 ft/sec. The first car overtakes the second car and
2
couples with it. Calculate the final velocity of the two cars.
Solution:
The final velocity (v ) can be easily calculated using Equation 3-8.
f
