NTA Abhyas JEE Main2020PhysicsMechanical Properties of FluidsPractice
Water flows out of a big tank along a tube bent at right angles; the inside radius of the tube is equal to r = 0 . 50 cm . The length of the horizontal section of the tube is equal to l = 22 cm . The water flow rate is Q = 0 . 50 L s - 1 . Find the moment of reaction forces of flowing water, acting on the tube's walls, relative to the point Q .
Options
- Aρ Q 2 l π r 2
- Bρ Q ⁡ 2 l ⁡ π r ⁡
- C- ρ Q ⁡ 2 l ⁡ π r ⁡ 2
- Dρ Q ⁡ l ⁡ π r ⁡ 2
Correct answer
A. ρ Q 2 l π r 2
Step-by-step solution
Consider only bend part of the tube. The change in momentum of mass Δm of liquid as it passes through the bend, Δ P → = P → f ⁡ - P → i ⁡ = Δ m ⁡ v ⁡ i ^ - Δ m ⁡ v ⁡ - j ^ = Δ m ⁡ v ⁡ i ^ + Δ m ⁡ v ⁡ j ^ ∴ F → = Δ P ⁡ Δ t = v ⁡ Δ m ⁡ Δ t i ^ + v ⁡ Δ m ⁡ Δ t j ^ = v ⁡ ρ S ⁡ Δ L ⁡ Δ t i ^ + v ⁡ ρ