Given,
Initial maximum hight obtained by the ball= 120 m.
By using projectile motion equation (maximum hight)
H1=u2sin2452g=120
u24g=120 …. (i)
When half of kinetic energy is lost v = u√2
so again , H2=(u√2)2sin2302g=u216g...… (ii)
From (i) and (ii)
H2=14[u24g], (where, u24g=120 from eq. (1))
so, 14×(120)=30 m
Hence, the maximum hight after the collision will be 30 m.