BERNOULLI EFFECT

BERNOULLI’S EFFECT
State the observations made when air flows above.
a) The curved surface of a hemisphere.


b) The flat surface of the hemisphere.


c) A spherical object.


Draw the streamlines over the curved surface of a hemisphere resting on its flat surface.



Explain the observations made in Q2.


In certain spray bottle water breaks into sprays as it flows out when its velocity reaches 8m/s. If water flows through a tube of internal diameter of 0.4 cm with a velocity of 0.02m/s and emerges from a jet as a spray, calculate the maximum possible diameter of the jet.


The figure below represents an advertisement board commonly displayed at fuel stations. The board rotates freely when wind blows over it.






a) State the direction of rotation of the board according to an observer viewing directly from above the board.


b) Explain why the board rotates.


c) State whether the direction of rotation changes with the direction of the wind.


Water flows in a pipe with a velocity VP and leaves the tap with velocity Vt. If the internal diameter of the pipe is D, find an expression of the internal diameter d of the tap.


Explain why the walls of a house are likely to collapse inwards as the roof is blown off.


The figure below shows a looped tube with an inlet and out let through which water flows. The arm y has the same diameter as the outlet X while Z is wider.





Treating the loop as horizontal, compare the levels of water in the vertical limbs.
a) A and C
b) Band C
c) A and B
d) C and D
With the aid of a well labeled diagram, explain what is likely to be observed when a strong wind blows.
a) through a tunnel


b) Between two close parallel walls.

Give two reasons why the velocity of wind is low near the ground.


A strong wind blows over the roof of a building.
a) What is likely to happen to the roof? Explain.


b) Suppose the wind blows across the ridges of the roof, state and explain whether in this case the ridges have an advantage or a disadvantage.


c) What would be the effect of leaving a small gap between the roof and the wall? Explain.


Describe a suitable method not involving a dipstick; you would use to get an idea about the variation in depth of a river along its course.


The figure below shows the path taken by a fluid particle for a fluid flowing from region A to C.



a) Give a possible reason for the loop at B.

b) Would you expect a loop to form at B if the direction of flow is reversed? Explain.

Explain how the rotation of blades at the top of a helicopter enables it to take off.


Complete the figures below to show the streamlines for.



a) a fluid flowing past a stationary object and


b) An object moving through a still fluid.


State three factors that determine whether a fluid flow is streamline or turbulent.


State two disadvantages of turbulent flow, referring to the flight of an aero plane.


The figure below shows the cross-sectional side view of a wing for an aero plane taking off.






Mark on your diagram three forces acting on the wing indicating their directions.
State two advantages of streamlined shapes.


A certain section, S, a river is 8m wide and 1m deep and water flows at the rate of 18m3 per second. At another section, Q, of the river, velocity is found to be 1.5m/s.
a) Calculate the velocity of water at section S.


b) Give two possible reasons why velocity at Q is 1.5m/s instead of the value at S.


c) Calculate the velocity of the river at a section where
I) depth is 0.8 m and width is 8m


II) Width is 4 m and depth is 2 m.