# Fluid Mechanics Questions and Answers – Force Exerted by a Jet on a Stationary Flat Inclined Plate

This set of Fluid Mechanics written test Questions & Answers focuses on “Force Exerted by a Jet on a Stationary Flat Inclined Plate”.

1. Force exerted by a jet on a stationery plate happens in how many cases?
a) 3 cases
b) 2 cases
c) 1 case
d) Nil

Explanation: Force exerted by a jet on a stationery plate happens in three cases. The three cases are classified depending on their position. The three cases are when plate is vertical, plate is inclined and plate is curved with respect to the jet.

2. Force exerted by a jet on a moving plate happens in how many cases?
a) 3 cases
b) 2 cases
c) 1 case
d) Nil

Explanation: Force exerted by a jet on a moving plate happens in three cases. The three cases are classified depending on their position. The three cases are when the plate is vertical, plate is inclined and plate is curved with respect to the jet.

3. In a stationery vertical plate, the jet after striking the plate will move _______
a) In opposite direction
b) Along the plate
c) Perpendicular to the plate
d) Parallel to the plate

Explanation: In a stationery vertical plate, the jet after striking the plate will move along the plate. It moves with respect to the angles that are developed with the plate.

4. At what angle does the jet deflect after striking a stationery vertical plate?
a) 30
b) 60
c) 90
d) 0

Explanation: In a stationery vertical plate, the jet after striking the plate will move along the plate. It moves with respect to the angles that are developed with the plate. Hence, after striking the plate it will get deflected at an angle of 90 degrees.

5. The velocity component after striking the surface will be________
a) One
b) Zero
c) Infinity
d) Negative

Explanation: In a stationery vertical plate, the jet after striking the plate will move along the plate. It moves with respect to the angles that are developed with the plate. The velocity component after striking the surface will be zero.
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6. Which among the following is the formula for Force when it strikes the plate?
a) pav2
b) pav
c) pa
d) maE

Explanation: The rate of change of momentum in the direction of the force is given by the formula pav2. Where p = Density of the fluid flow, a = acceleration of the fluid particle and v= velocity of the fluid flowing.

7. To derive pav2, we take final velocity minus the initial velocity.
a) True
b) False

Explanation: The rate of change of momentum in the direction of the force is given by the formula pav2. Where p = Density of the fluid flow, a = acceleration of the fluid particle and v= velocity of the fluid flowing. To derive pav2, we take initial velocity minus the final velocity.

8. The mass of water per sec striking the plate is_________
a) pav2
b) pav
c) pa
d) maE

Explanation: The mass of water per sec striking the plate is given by pav. Where p = Density of the fluid flow, a = acceleration of the fluid particle and v = velocity of the fluid flowing. Thus, the correct option is pav.

9. Which among the following is formula for force when it acts along the direction of flow?
a) pav2Sin2θ
b) pav Sin2θ
c) pa Sin2θ
d) maE Sin2θ

Explanation: When a force can be resolved into two components, one in the direction of the jet and the other perpendicular to the jet. The formula for force when it acts along the direction of flow is equal to pav2 Sin2θ.

10. Which among the following is a formula for force when it acts perpendicular to the direction of flow?
a) pav2 SinθCosθ
b) pav Sin2θ
c) pa Sin2θ
d) maE Sin2θ

Explanation: When a force can be resolved into two components, one in the direction of the jet and the other perpendicular to the jet. The formula for force when it acts perpendicular to the direction of flow is equal to pav2 SinθCosθ.

11. A jet strikes a curved plate at its ______
a) Sides
b) Surface
c) Centre
d) Does not strike

Explanation: A jet strikes a curved plate at its center. Force exerted by a jet on a stationery plate happens in three cases. The three cases are classified depending on their position. The three cases are when plate is vertical, plate is inclined and plate is curved with respect to the jet.

12. During a weak jump, the value of Froude lies in between________
a) 1 to 2.5
b) 2.5 to 3.5
c) Less than 1
d) Zero

Explanation: Weak jump is a jump that takes place, when the Froude’s number lies in between 1 to 2.5. The surfaces that result due to weak jump have a very little energy dissipated. Thus, option 1 to 2.5 is the correct one.

13. During an oscillating jump, the value of Froude lies in between________
a) 1 to 2.5
b) 2.5 to 4.5
c) Less than 1
d) Zero

Explanation: An oscillating jump is a jump that takes place when the Froude’s number is in between 2.5 to 4.5. During this jump, the jet water at the entrance of the jump fluctuates. It fluctuates from the bottom of the channel to the top of the channel.

14. A jet after striking a smooth plate comes out with a __________ velocity.
a) Increased
b) Decreased
c) Same
d) Zero

Explanation: Force exerted by a jet on a stationery plate happens in three cases. The three cases are classified depending on their position. After it strikes a smooth plate, its velocity remains the same.

15. Component of velocity in direction of jet is -VCosθ
a) True
b) False

Explanation: Component of velocity in direction of jet is -VCosθ. The negative sign indicates the that the taken velocity at the outlet is opposite to the jet of water coming out from the nozzle. Thus, it is true.

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