What is the method for calculating velocities in a perfectly elastic collision?

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In a perfectly elastic collision, both momentum and kinetic energy are conserved. The initial velocity of a 1kg ball, calculated from its potential energy after falling 1.2m, is 4.85 m/s. Using the conservation of momentum and the equation for kinetic energy conservation, two equations can be established to solve for the final velocities of the balls. The final velocities determined are V1 = -0.97 m/s for the 1kg ball and V2 = 3.88 m/s for the 1.5kg ball. The method involves applying Newton's law of restitution alongside these conservation principles to find the final velocities.
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1. a 1kg ball traverse a frictionless tube. the ball after falling through a height of 1.2m, strikes a1.5kg ball which initially at rest. find the velocities of the two balls, if the collision is perfectly elastic. V1= -0.97m/s V2= 3.88m/s



2. i found out the initial velocity of 1kg ball
mgh = 1/2mv^2
1(9.81)1.2= 1/2(1)v^2
v= 4.85m/s

after that, i use mu+mu = mv+mv
1(4.85)+ 1.5(0)= 1v +1.5v2

after that, what should i do to get the answer?
help me...please...
 
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In a perfectly elastic collision KE is also conserved. This gives you a second equation in the two unknowns (velocities of the balls after collision).
 
what u mean?
but i use Newton's law of restitution to get the answer.
e=(v1-v2)/(u2-u1)

-4.85=v1-v2---------second equation
and i finally get the answer.
 
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