Blocks of mass 4.5 kg and 3.5 kg hang from the two ends of a light string over a smooth pulley…

Step 1. Acceleration. $a = \dfrac{(4.5 - 3.5)\ \text{kg} \times 9.8\ \text{m/s}^2}{4.5\ \text{kg} + 3.5\ \text{kg}} = \dfrac{9.8\ \text{N}}{8.0\ \text{kg}} = 1.225\ \text{m/s}^2$.

Step 2. Tension. The lighter block rises: $T = 3.5\ \text{kg} \times (9.8\ \text{m/s}^2 + 1.225\ \text{m/s}^2) = 38.59\ \text{N}$.

Step 3. Speed. $v = \sqrt{2 \times 1.225\ \text{m/s}^2 \times 1.2\ \text{m}} = 1.71\ \text{m/s}$.