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Physics Need help with Physics with trigonometry problems ?


New member
Dec 10, 2018
3) Hurricane Michael had horizontal winds of Vout = 69 m/s (155 mph). Pair = 1.29 kg/m3. A building with a flat, horizontal roof, Aroof = 200 m2, and Vin = 0 m/s.

a) What is the pressure difference, Pin - Pout on the roof. Assume Yin = Yout.

b) What is the force acting on the roof, and what is the direction of this force ?

c) What is this force in pounds ? 1 N = .225 lb.

After the storm, it is found that a small object has been driven into the water tower. The water level inside the water tower is 12 meters above the ground. The height of the hole is 9 meters above the ground. The object is removed and water sprays out.

d) Considering the hole and the tower, what is the speed of the water coming out of the hole ? Assume Vin = 0 and Pin = Pout = Patm.

e) If the hole is 9 meters above the ground, how long does it take the water to hit the ground ?

f) With the speed the water has, and the time to hit the ground, how far does it travel horizontally ?

So, I'm not sure if I did it right but what I did for part A was use the Bernoulli's equation:

P1 + 1/2pv1= P2 + 1/2pv2

Delta P (P2-P1)= 1/2pv21 - 1/2pv22

Delta P = 1/2p (V21 - V22)

Delta P = 1/2 (1.29 kg/m3) (692 m/s - 02 m/s)

Delta P = 3070 PA

I'm not sure if I'm correct though so I didn't really attempt to do the other questions to this problem in case I'm wrong.. I'll gladly appreciate it if someone could help me out.

Klaas van Aarsen

MHB Seeker
Staff member
Mar 5, 2012
Hey gamergirlxoxox! Welcome to MHB! ;)

You are entirely correct.

Here's a video where it's explained:


New member
Dec 10, 2018
Thanks ! I think I can probably figure the rest out now