Two freight trains, each of mass 5 times 10^6 kg (5000 metric tons) travel in op

Question

Two freight trains, each of mass 5 times 10^6 kg (5000 metric tons) travel in opposite directions on the same track with equal speeds of 42 m/s (about 100 miles/hr). They collide head on and come to rest. Calculate in milligrams the kinetic energy for each train 1/2 mv^2 before the collision. (Note Newtonian expression is fine to use for such a low speed). After the collision, the mass of the trains plus the mass of the track plus the mass of the roadbed has increased by what number of milligrams? Neglect energy lost in the forms of sound and light.

Explanation / Answer

a)

kinetic energy of train = 0.5 mV^2

KE = 0.5 x 5 x10^6 x 42x42

KE = 4410000000

KE = Mc^2

so

M = 0.049 milligram

b)

mass is increased by 2 M

mass increased = 2 x0.049 = 0.098 milligram

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.