AL physics問題,,煩請高手幫幫手

1. Using Bernoulli's Principle.

(1/2).(d).v^2 + p = (1/2).(d').(v)^2 + p'
where d and p are the reference density and pressure, and d' and p' are the new density and new pressure respectivle.
v is the speed of air (assume to be constant)

hence, pressure difference (p - p') is,
p - p' = (v/2).(d' - d)
It is thus clear that when d' increases (d' > d), the pressure difference (p-p') increases.

However, on an aerofoil (air wing), it should be the speed of air passing over the top of the aerofoil increases rather the the air density increases.

2. Your question is not clear. Don't know you mean "work done by what???". You did not mention any physical process.

The equation : Potential energy (PE) change = work done is generally true. The potential energy in space arises because of gravitational attraction from a nearby planet (or star).