Answer:
177.5 m/s (*)
Step-by-step explanation:
Applying the conservation of momentum for elastic collisions, with:
m1 = mass of car: 800 kg
v1 = velocity of car (unknown)
m2= mass of truck: 5000 kg
v2 = velocity of truck -40 m/s (opposite direction with car)
v2' = velocity of truck after collision = -10m/s (opposite direction with car)
=> m1 x v1 + m2 x v2 = (m1 + m2)v2'
=> 800 x v1 + 5000 x (-40) = (800 + 5000) x (-10)
<=>800 x v1 = 200000 - 58000
<=> 800 x v1 =142000
<=> v1 = 177.5 m/s
This result looks like unreal.
In fact, it would be more reasonable if the velocities of truck before and after collision are 40km/h and 10km/h respectively. Hence, the result is 177.5 km/h.
Hope this helps!
