Physics for Scientists and Engineers: A Strategic Approach with Modern Physics (4th Edition)

$T = 170~N$
We can use the equation for centripetal force to find the tension in the rope at the lowest point; $\sum F = \frac{mv^2}{r}$ $T-mg = \frac{mv^2}{r}$ $T = \frac{mv^2}{r} + mg$ $T = \frac{(10.2~kg)(5.5~m/s)^2}{4.5~m} + 100~N$ $T = 170~N$