Answer:
v = 21.409 m/s
Step-by-step explanation:
Given data:
Total weight of the platform and weight together, W = 900 N
Diameter of the water jet = 5 cm = 0.05 m
Now,
the force exerted by the water jet is balancing the platform
also,
Force exerted by the water jet = ρAv²
where,
ρ is the density of the water = 1000 kg/m³
A is the area of the outlet of the jet =

or
A = 0.00196 m²
v is the velocity of the jet
thus,
W = ρAv²
or
900 = 1000 × 0.00196 × v²
or
v = 21.409 m/s
Hence, the velocity of the jet is 21.409 m/s