Answer :
Answer: 12cm
Explanation:
Since first ball is raised to a height h1= 6cm, it gains a potential energy(PE1). On release, this PE1 is converted to kinetic Energy (KE1). This KE1 impact it energy on ball 2 ans it rise also. Since collision is elastic.
KE1 = KE2 ....> PE1 = PE2
m1 ×g × h1 = m2 × g× h2
h2 = m1×h1/m2
h2 = 0.4 × 0.06/0.2
h2 = 0.12m = 12cm