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 .

Scale reading for no wind

Explanation:

From the question we are told that

Area

Weight of board

Velocity

Density of air

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

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

Therefore

Scale reading for no wind W'

Scale reading for no wind W'=60N

c. newton's third law of motion