Answer:
v = 5.5 m / s
Explanation:
For this exercise let's use Newton's second law, where the acceleration is centripetal
F = ma
a = v² / r
Before starting we reduce the mass to the SI system
m = 250 g (1 kg / 1000g)
m = 0.250 kg
Let's calculate the velocity for when the forces equal to T = 8.7N
T = m v² / r
v² = T r / m
v = √ T r / m
v = √ (8.7 0.87 /0.250)
v = 5.5 m / s