Question

A 1200 kg car travelling with a speed of 25 m/s in
an easterly direction crashes into the rear end of a
9000 kg truck moving in the same direction at 20
m/s. The velocity of the car right after the collision
is 18 m/s to the east. (a) What is the velocity of
the truck right after the collision? (b) How much
mechanical energy is lost in the collision? Account
for this loss in energy.​

Answer 1

Explanation:



Waheed9 years ago

momentum 

m1 v1 + m2 v2 = m1' v1' + m2' v2' 

1200*25 + 9000*20 = 1200*18 + 9000*v2' 

v2' = (1200*25 + 9000*20 - 1200*18 ) /9000

v2' = 20.933 m/s..................................ans 

Loss in K.E. = K.E. initially - K.E. finally 

= 0.5 * ( 1200*25^2 + 9000*20^2 - 1200*18^2 - 9000*20.933^2) = 8742.8 N-m................ans