Answer:10 m/s
Step-by-step explanation:
Given
Tarzan runs at v=8 m/s
Height of branch is h=5 m
Conserving Energy as it is constant at bottom point and on the branch
Energy at bottom is equal to kinetic Energy of Tarzan

Energy at top

Equate



Thus velocity needed to reach branch is 10 m/s which is greater than 8 m/s so Tarzan will not make it to branch.
So he need to run at atleast 10 m/s