Question

A horizontal board of negligible thickness and area 2.0 m2 hangs from a spring scale that reads 80 N when a 4.0 m/s wind moves beneath the board. The air above the board is stationary. What does the scale read when the wind stops? The density of air is 1.25 kg/m3 .

Answer 1

Answer:

Scale reading for no wind $W'=60N$

Explanation:

From the question we are told that

Area $A= 2.0 m^2$

Weight of board $W=80$

Velocity $V=4.0m/s$

Density of air $\delta= 1.25 kg/m3 .$

Generally the equation for pressure difference by Bernoulli equation is mathematically given by

  $dP=\frac{1}{2}pv^2$

  $dP=10Pa$

Generally force acting on the board by air is mathematically given by

$F=\triangle PA$

$F=(10)2=>20N$

Therefore

Scale reading for no wind W'

$W'=W-F\\W'=80-20$

$W'=60N$

Scale reading for no wind W'=60N