What is the velocity of the yellow disk after the collision?Two shuffleboard disks of equal mass, one orange and the other yellow, are involved in...

In a perfectly elastic collision, the final momentum of
the bodies that collide is the same as their initial
momentum.

Momentum is given as mass*velocity. Let us take
the mass of both the disks to be M.

Here, initially the
yellow disk is at rest and the orange disk is moving at 7.05 m/s. The total momentum of
the two disks is 0*M + 7.05*M.

The collision of the two
disks is perfectly elastic and after the collision the orange disk comes to rest. Let
the velocity of the yellow disk be V. So the total momentum is M*V +
M*0.

Now M*V + M*0 = 0*M +
7.05*M

=> M*V =
7.05*M

=> V = 7.05
m/s

The velocity of the yellow disk after the
collision is 7.05 m/s