Advertisements
Advertisements
प्रश्न
Explain why To keep a piece of paper horizontal, you should blow over, not under, it
उत्तर १
When air is blown under a paper, the velocity of air is greater under the paper than it is above it. As per Bernoulli’s principle, atmospheric pressure reduces under the paper. This makes the paper fall. To keep a piece of paper horizontal, one should blow over it. This increases the velocity of air above the paper. As per Bernoulli’s principle, atmospheric pressure reduces above the paper and the paper remains horizontal.
उत्तर २
When we blow over the piece of paper, the velocity of air increases. As a result, the pressure on it decreases in accordance with the Bernoulli’s theorem whereas the pressure below remains the same (atmospheric pressure). Thus, the paper remains horizontal.
APPEARS IN
संबंधित प्रश्न
In a test experiment on a model aeroplane in a wind tunnel, the flow speeds on the upper and lower surfaces of the wing are 70 m s–1and 63 m s–1 respectively. What is the lift on the wing if its area is 2.5 m2? Take the density of air to be 1.3 kg m–3.
Figures (a) and (b) refer to the steady flow of a (non-viscous) liquid. Which of the two figures is incorrect? Why?
Water is flowing through a long horizontal tube. Let PA and PB be the pressures at two points A and B of the tube.
A large cylindrical tank has a hole of area A at its bottom. Water is poured in the tank by a tube of equal cross-sectional area A ejecting water at the speed v.
What is the basis of Bernoulli’s principle?
A large number of liquid drops each of radius 'a' are merged to form a single spherical drop of radius 'b'. The energy released in the process is converted into kinetic energy of the big drop formed. The speed of the big drop is [p = density of liquid, T = surface tension of liquid] ____________.
Which of the following is NOT an example of the application of Bernoulli's principle?
The working of venturimeter is based on ______.
If p0 = 1.03 × 105 Nm–2, ρ0 = 1.29 kg m–3 and g = 9.8 ms–2, at what height will the pressure drop to (1/10) the value at the surface of the earth?
In the widest part of the horizontal pipe, oil is flowing at a rate of 2 m/sec. The speed (in m/s) of the flow of oil in the narrow part of the tube if the pressure difference in the broad and narrow parts of the pipe is 0.25 ρoilg, is ______ m/s.
