Answer:
20 metric tons
Explanation:
Using the Principle of Conservation of Linear Momentum which states that the total momentum of a system is constant in any direction in which no external force acts.
momentum before collision= momentum after collision
mathematically expressed as
m1u1 + m2u2 = m1v1+m2v2 =0
where:
m1= mass of rolling freight car = 10 metric tons = 10Mg
1 ton = 1000kg= 1Mg
u1 =initial velocity of freight car = 108km/h,
m2 = mass of stationary freight car = ?, this the unknown we are finding
u2 = initial velocity of
m2 = 0, because it is at rest,
v1= final velocity of m1,
v2= final velocity of m2
since they move together in the same direction they share a common final velocity as such
v1=v2= 36km/h
substituting valves in expression give
m1u1 + m2u2 = m1v1 + m2v2= 0
10Mgx 108km/hr + m2 x 0 = 10Mg x 36km/h + m2x36km/h
1080( Mg x km/hr) + 0 = 360 (Mg x Km/h) + 36m2 (km/h)
1080 (Mgx km/hr) - 360(Mg x km/h) = 36m2 (km/h)
720(Mg x km/h) = 36m2 (km/h)
divide both side by 36 (km/h) gives
m2 = 20Mg =20 metric tons
