Homework Help: physics

Posted by Kinetic Energy on Friday, February 4, 2011 at 2:55am.

In a head-on, inelastic collision, a 4000 kg truck going 10 m/s east strikes a 1000 kg
car going 20 m/s west.
(a) What are the speed and the direction of the wreckage?
(b) How much kinetic energy is lost in the collision?

physics - drwls, Friday, February 4, 2011 at 3:06am
a) It is a head-on collision.
Momentum is conserved.
The final momentum (measured positive east) is 4000*10 -1000*20 = 20,000 kg m/s

Set that equal to (M1 + M2)*Vfinal
and solve for Vfinal.

b) Compute the (1/2)M1*V1^2 + (1/2)M2*V2^2 with
(1/2)(M1+M2)Vfinal^2
The latter will be less. The firrence will be the kinetic ene4rgy lost./

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