# Search results

1. ### Pascal triangle?

if we toss 4 coins and we want to know the probability of having 3 heads we can easily calculate that using pascal triangle . I want to know if we have an Urn that contain 3 balls : 1 black , 1 red, 1 yellow. and we want to draw 3 balls , but when we draw the first ball we put it back in the...
2. ### Tidal force

some telecomunication satellites in orbits are made to be kept oriented in a certain way where their reception and broadcasting antenna or whatever is called should awalys face the earth so while orbiting the satellite has to be interlocked with the surface of the earth. My question is: can the...
3. ### Pressurised tank

I have a system that consist of a water tank a pump that is pumping into a pressuirsed tank at 100 GPM and another pump at the outlet of the pressurized tank that is pumping to the 6th floor , my question is can I consider the 2 pumps as 2 pumps in series ? , my second question is : is there a...
4. ### Transient heat transfer in heat exchangers

Considering an engine generating thermal heat at 140 kw and when the generation starts the thermal equilibrium of the engine will be distrubed , a radiator is installed to cool the engine this radiator cool the engine through flow of water and water is cooled inside a heat exchanger with air ...
5. ### Bernoulli and darcy equation in split flow system

Refering to the image uploaded can we say by applying bernouli equation and darcy equation the following : Pa/(guamma) + Va^2/2.g + Za - (head loss in pipe ab using darcy equation )-(head lossin pipe bc using darcy equation) = Pc/(guamma) + Vc^2/2.g + zc . ?? and the same thing between...
6. ### Electric and magnetic field

In the case of "Light" when it is considerd as an electromagnetic wave , this wave consist of an electric field and magnetic field oscillating all the time when the electric field is maximum the magnetic field is minimum and vice versa , my question is : what is the mechanism that create such...
7. ### System head curve for tree piping system

as we know to draw the system curve of a piping system we have to change the value of Q total and get a head for each value we put in the following equation : H=Hstatic +Kq^2 where K is the sum of major and minor losses. what if we have a piping system that have many branches "tree -system"...
8. ### City Water supply pressure

In plumbing we need to know the pressure in the city main supply , my question is how can the city give us the minimum pressure of its supply for our building lets say before pluging in our whole plumbing system to the city main line ??? usually the pressure at a node is determined when it...
9. ### Hazen william Vs Darcy (pipe sizing)

if we have a pipe system like in the figure below where a pump exist in the system in order to deliver 200 gpm of water from the tank "A". we need to deliver 150 gpm from "C" and 50 gpm from "D" usually we use the pipe flow chart of william hazen in order to size each pipe according to its flow...
10. ### Pipe flow

If we have an open pipe system that will deliver in total 200 gpm divided in 2 pipes the first pipe is 50 gpm and the second is 150 gpm , the 2 pipes have the same length , if we want to size the pipes where both pipes will have the same diameter , if we do that through william hazen eqution...
11. ### Centripital force on 3d bodies

I have created such a thread in the past but it was misinterpreted and I havent been given the help I needed , this time I shall explain more about what is going wrong through a figure . sorry for my bad english. topic: when a 3d body is going at constant velocity in a straight line and...
12. ### Latent heat of vaporization Water thermodynamic

Latent heat of vaporization "Water" thermodynamic -first of all I want to know if the "latent heat of vaporiasation " of water is related to the initial pressure of water ? -If LHV of water is variable with the variation of pressure , how can we calculate the heat needed to vaporise a...
13. ### Gear box design

If I have a designed gear box that needs a motor to run , and according to my calculations the input power for the gear box must be 10 Kw at 10 r.p.s must I chose a motor with the same input specifications ? when I buy a motorwith certain specifications like : 10 kw 3000 R.P.M , does these...
14. ### 2 acceleration components

if a body that is going in space in a straight line and suddenly 2 forces acts on it the first with the motion direction and the other is perpendicular to the motion direction , would the object start to go in circles ??? or it will change its direction of motion and will keep going sideways ...
15. ### Curve trajectory

I wanna know whether this analysis in the image is correct or no ,and if no pleas I want u to explain me the reason thank you ..
16. ### Orbital motion

I want to know the difference between the 2 types of rotations shown in the picture attached . planetary orbiting are similar to the second figure in the picture attached , all i wanna know what is the difference between the 2 figures .
17. ### Confusion between simultanety and time dialation

Let events 1 and 2 occur at and in frame S. In frame S' they occur at https://www.physicsforums.com/latex_images/18/1880804-3.png [Broken] https://www.physicsforums.com/latex_images/18/1880804-3.png [Broken] [PLAIN]https://www.physicsforums.com/latex_images/18/1880804-4.png [Broken]...
18. ### Confusion is speed of light

Consider you (A) are moving at the speed of 180 000 km/s and another person (B) moving at an opposite direction to you at 100 000km/s. what would be the speed of the either relative to each other? Both would appear to be approaching each other at the speed of sum of both of their speeds. (i.e...
19. ### Torque and power

how can we say that torque is equal to power / angular velocity though we know that torque is equl to I x (change of angular velocity over time ). and how can we relate torque to (angular velocity) , as we know that a rotating gear at constant angular velocity has no torque on it or bettter...
20. ### Coriolis issue

according to the figure attached below , do we have a coriolis acceleration on the slider and why ? why cant we say that it is a centripital acceleration ??? I want to know the difference between coriolis accelration and centrepetal acceleration , cause As I know , coriollis...
21. ### Centrifuagal and centripital force

-in balancing masses , why do we always say that we need to put a mass in a rotating disk that produce a centrifugal force that is equal to the unbalanced mass ? -cant we say that a centripital force of a certain rotating mass is euqal to a centrifugal force of the same mass but in different...
22. ### Moment issue

please explain to me this phenomena (Details in the picture attached) - after answering my 2 questions , I would like to make a modification in the picture , the modification is : shifting the force F 1 to the left for 0.5 m , after shifting it 0.5 m would we have a moment at "B" and at "A" ...
23. ### A confusing torque phenomena

to be able to understand my point of view please check this picture which I attched>> the question is in the picture please check it thanks