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Home Q & A Board Science-Related Homework Help Physics
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leroy3 leroy3
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11 years ago
A 9000kg car moving at 3 m/s strikes a stationary 5000kg railroad care.
What is the KE of the 9000kg car before the collision and the momentum before the collision?

If the two cars couple and move off together after the collision, what is their velocity?
Help!
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#1
11 years ago
Momentum of Car before collision = 9000x3 = 27000 kg m s^-1
KE of car before collision = 0.5x9000x3^2 = 40500 J
Let the common velocity just after they collide and couple be V, then
(9000+5000)V = 27000 + 0 or V  = 1.928 m/s by equating the total momentum of the car and rail road car just before collision and after it.
wrote...
#2
11 years ago
for the KE and momentum question:
KE = (1/2)*m*v^2
and
p = m*v

for the final inelastic collision question, conserve momentum.
initial momentum = final momentum.
m1*v1 + m2*v2 = (m1+m2)*v_final
v2 = 0 by definition
solve for v_final.

as all masses are in kg and all speeds are in m/s, this is trivial.
plug and play...

cheers
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