Posted by Lui on .
A 6.0 g coin moving to the right at 21.0 cm/s makes an elastic headon collision with a 20.0 g coin that is initially at rest. After the collision, the 6.0 g coin moves to the left at 12.5 cm/s.
a.) Find the final velocity of the other coin in centimeters.
b.) Find the amount of kinetic energy transferred to the 20.0 g coin.

Momentum 
Elena,
m1= 6•10^3 kg, v1 = 0.21 m/s,
m2 = 20•10^3 kg, v2 = 0,
u1 =0.125 m/s,
u1 =? KE2 =?
m1•v1 =  m1•u1 +m2•u2,
u2 =2•m1•v1/(m1+m2) = 2•6• 10^3•0.21/26•10^3 =0.097 m/s
KE2 =m2•u2²/2 =20•10^3•(0.097)²/2 =9.41•10^5 J.