Answer:
The fraction of the total initial kinetic energy is lost during the collision is 
Explanation:
Given that,
Mass of one piece = 300 g
Speed of one piece = 1 m/s
Mass of other piece = 600 g
Speed of other piece = 0.75 m/s
We need to calculate the final velocity
Using conservation of energy

Put the value intro the formula



We need to calculate the total initial kinetic energy
Using formula of kinetic energy

Put the value into the formula


We need to calculate the total final kinetic energy
Using formula of kinetic energy

Put the value into the formula


We need to calculate the energy lost during the collision
Using formula of energy lost


Hence, The fraction of the total initial kinetic energy is lost during the collision is 