FM - VEDA -IMPACT OF JECT & HYDRAULIC MACHINES

The force exerted by a jet of water on a moving vertical plate, in the direction of motion of plate is given by

When a jet strikes a stationary curved vane at the center and is deflected symmetrically, the resultant force is:

• Zero
• 2ρaV²
• ρaV²(1 + cosθ)
• ρaV²(1 - cosθ)

Answer explanation

Resultant force = ρaV²(1 + cosθ), for symmetric deflection.

In case of a jet striking a moving curved vane tangentially, the work done is maximum when vane velocity is:

• Equal to jet velocity
• Half of jet velocity
• One-fourth jet velocity
• Equal to 2V

Answer explanation

Maximum work done when vane velocity = V/2.

When a jet of fluid strikes a stationary vertical plate normally, the force exerted on the plate is proportional to:

• Area of plate
• Velocity of jet
• Square of velocity of jet
• Mass of jet

Answer explanation

The force F = ρaV², so force is proportional to V².

In impact of jet, if a plate is moving in the direction of jet, the relative velocity is:

• Sum of plate and jet velocity
• Jet velocity
• Difference of jet and plate velocity
• Zero

Answer explanation

Relative velocity = V - u (jet velocity - plate velocity).

In Pelton turbine, the jet strikes:

• Axially

• Curved vane at center
• Tangentially at splitter
• Radially outward

Answer explanation

Jet hits tangentially at splitter in Pelton turbine.

The impact of jet theory is based on the principle of:

• Pascal’s Law
• Newton’s Second Law
• Bernoulli’s Theorem
• Archimedes’ Principle

Answer explanation

Impact theory uses Newton’s Second Law: F = Δ(mv)/Δt.

A Pelton wheel is ideally suited for:

• High head and low discharge
• High head and high discharge
• Low head and low discharge
• Medium head and medium discharge

Answer explanation

Pelton wheel is suitable for high head and low discharge due to its impulse action.

The channel or pipe which carries water away from the power house after it has been passed through the turbine is:

• Main canal
• Penstock
• Regulator
• Tail-race

Answer explanation

Tail-race carries water away from turbine after energy extraction.

Name the ratio of power available at the shaft of a turbine to the power delivered by water to the runner.

• Volumetric Efficiency
• Overall Efficiency
• Mechanical Efficiency
• Hydraulic Efficiency

Answer explanation

Mechanical efficiency = shaft power / runner power.