Answer:
v = 3.84 m/s
Step-by-step explanation:
In order for the riders to stay pinned against the inside of the drum the frictional force on them must be equal to the centripetal force:

where,
v = minimum speed = ?
g = acceleration due to gravity = 9.81 m/s²
r = radius = 10 m
μ = coefficient of friction = 0.15
Therefore,

v = 3.84 m/s