physics
posted by Damon .
i need some help wih this, thanks!!
Blocks A and B are moving toward each other along the x axis. A has a mass of 2.0 kg and a velocity of 50 m/s ( in the positive x direction ), while B has a mass of 4.0 kg and a velocity of 25 m/s ( in the negative x direction). They suffer an elastic collision and move off along the x axis. After the collision the velocities of A and B, respectively are:
a 50 and 25 m/s
b 50 and 25 m/s
c 25 and 50m/s
d 25 and 50 m/s
e 25 and 50 m/s
Momentum is conserved:
2*50+4*(25)=0 so the final momentum has to be zero. Which also means they are going in opposite directions, which means that A has a neg v eloctiy, and B a positive velocity. Answers A, c fit that. Now, a is zero momentum. And c is zero momentum.
Conservation of energy:
Initial energy: 1/2 2*50^2 + 1/2 4*25^2 equals something. You can see that answer a is the only answer possible.
thankyou
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