(2300 lbm)(29 ft/sec)
(2800 lbm)(11 ft/sec)
Force and Motion
If the initial velocities of the two objects (v and v ) are known, then the final velocity (v ) can
be calculated by rearranging Equation 3-10 into Equation 3-11.
Consider that the railroad cars in Figure 1 have masses of m = 2300 lbm and
m = 2800 lbm. The first car (m ) is moving at a velocity of 29 ft/sec and the second car
(m ) is moving at a velocity of 11 ft/sec. The first car overtakes the second car and
couples with it. Calculate the final velocity of the two cars.
The final velocity (v ) can be easily calculated using Equation 3-8.