Question

A 15,000 kg railroad freight car travels on a level track at a speed of 2.5 m/s. It collides and couples with a 25,000 kg second car, initially at rest and with brakes released. What is the speed of the two cars coupled together after collision

Answer 1

Answer: 0.94 m/s

Step-by-step explanation:

Mass of the first car:

m1=15,000 kg

Speed of the first car:

v1=2.5 m/s

Mass of the second car:

m2=25,000 kg

`$$Apply the conservation of momentum.$$m_(1) v_(1)+m_(2) v_(2)=\left(m_(1)+m_(2)\right) v_(f)$$Substitute the values.$$\begin{aligned}(15000 * 2.5)+(25000 * 0) &=(15000+25000) v_(f) \\37500 &=40000 v_(f) \\v_(f) &=(37500)/(40000) \\&=0.9375 \\&=0.94 \mathrm{~m} / \mathrm{s}\end{aligned}$$`

Therefore, the speed of the two cars coupled together after the collision is 0.94 m/s