Well the trivial answer is zero, since there is indeed a "zero vector". Assuming you aren't allowed to use the zero vector you would need at least two. They would be antiparallel and of equal magnitude. (That is be pointing in opposite directions and have the same length)
According to the Bernoulli's equation,the pressure difference between the wide and narrow ends of the pipe is given by
Here, 
is the velocity of water through wide ends of cylindrical pipe and 
is the velocity of water through narrow ends of cylindrical pipe.
Given, 
Now from equation continuity,
.
Here, 
and 
are cross- sectional areas of wide and narrow ends of cylindrical pipe.
As pipe is circular, so
.
At the second point, the diameter is halved, which means the radius is also halved. Therefore,
Substituting these values with the density of water is 
in pressure difference formula we get.
Electromagnetic waves differ from mechanical waves in that they do not require a medium to propagate. this means that electromagnetic waves can travel not only trough air and solid materials, but also trough the vacuum of space.
It would <span>keep rolling without slowing down if no friction acted upon it.
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Answer:
to make calculation more easy to get
Explanation:
if you are using chart or calculate Thermodynamic problems you will not never solve this problem with out using data table for thermodynamic
