The maximum potential energy of a block executing simple harmonic motion is given by Umax=21mω2A2=25J
As, kinetic energy of particle executing SHM is KE=21mω2(A2−x2).So, kinetic energy of block KEat2A=21mv12=21mω2(A2−4A2)
⇒KE=21mω243A2=43(21mω2A2)
⇒KE=43×25=18.75J