Question

This question is about Bernoullis Principle (Air pressure). This is a long question and I want complete answers, so please take the time. Thanks for you <3

Assuming there are 29 drinking straws (1cm apart) below the empty small aluminium cans (which are 7cm apart) and you blow through a straw between the two cans.

a) What will happen? Observations in chart please

b) What would happen when you change the distance between the cans to 5 cm and 10 cm? Did the cans behaviour change with the distance seperating them?

c) Will altering the postion of the straw used to blow air between the cans alter the cans behaviour?

d) !!!!! Similar to the figure 12.2 draw arrows that represent airflow, the high pressure region, the low pressure region, and the motion of the cans. !!!!!

Answer 1

Part A) When we blow through the straw between the cans the cans move towards each other and this observation can be explained by using one of the very famous principle of fluid dynamics known as Bernoulli's principle which states that for an ideal fluid in streamline flow the sum of Kinetic energy, potential energy and pressure energy will remains constant or mathematically we can say that

$P +\frac{1}{2}\rho v^{2}+\rho gh = constnat$

as the both cans are at same height so we can reduce this equation as

$P +\frac{1}{2}\rho v^{2}= constnat$

So as we blow through the straw between the two cans the velocity of the air in the mid region increases and according to equation stated above as the velocity increases the pressure in the middle region decreases and the pressure on the outer edges will be more as compared to inner edges and hence the cans get pushed toward each other from high pressure zone to low pressure zone.

Part B) By changing the distance between the cans does not change the observation means the observation remains same only the impact will change and this will be similar when we are standing on a platform and a super fast train passes the passenger waiting on the platform got pushed towards the train. And passenger who are near the track get pushed with a greater force. But all will experience the same thing.

Part C) Changing the position of straw used to blow also does not change the observation but only impact get changed provided straw will not be very far away. Reason will remain same as explained above.

Part D) Air flow and region of low pressure and high pressure are as shown below

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