Hints: Exercise E4.7 (b)

[Jay Wang]

Start with the square root in Eq. (4.37), make the common denominator to be 2mr^2; simplify the numerator with Eq. (4.38), various relations in Eq. (4.12), you should reduce the whole thing to sqrt(ak/2) e sin(psi)/r. The integral over psi should be clear, and the final answer is obtained with Eq. (4.18).