Osmotic pressure =Hydrostatic pressure?in case of u shaped tube

There is a difference.

What is hydrostatic pressure?

The pressure that the fluid exerts on the walls of its container.

What is osmotic pressure?

The pressure required to prevent the flow of water across a semipermeable membrane via osmosis.

Pressure is force / unit area.

So, osmotic pressure is basically a pressure that is based on osmosis. First off, water can travel from low solute concentration to high solute concentration.

You really have to understand this because its counter-intuitive. We all know that osmosis is a type of simple diffusion. Right? So diffusion is movement of substance from high concentration to low concentration. So, why have I stated that water travels from low solute concentration to high solute concentration?

Okay, so think about it, water moves from a high water concentration to low water concentration. Now, if the concentration of water is high (solvent), that means that it must have little or few solutes. Hence, a low solute concentration. Solutes can represent anything like proteins, salts, just substances in low concentration within a solvent.

So hopefully you can see that water will rush into a solution from low solute concentration to high solute concentration.

Why is this important? Because osmotic pressure represents the pressure that forces capillaries to retain fluids within the capillary. Why? Because the capillaries contain a high solute concentration. Blood has lots of proteins like albumin and clotting factors and hemoglobin, etc. etc. So the interstitial fluid (which surrounds capillaries have a low solute concentration).

Now, hydrostatic pressure is the pressure exerted to push fluid outside the capillary. As far as what causes it. In terms of capillary, just know that hydrostatic pressure will push fluid outside capillaries.

Also, the difference in these two pressures (Osmotic and Hydrostatic) determine whether the net movement of fluid is outside or inside the capillary.

At the arterial end (fluid is pushed out) and that makes sense because it is full of oxygen, and nutrients that the cell needs. So now it needs to get to the tissues through the interstitial fluid.

So what do you think which pressure is greater at arterial end of a capillary?

Hydrostatic (sorry ruined the question) but Hydrostatic which pushes fluid out has to be greater that osmotic which pushes fluid back in.

At the venous end of capillaries, Osmotic is greater than hydrostatic because now the fluid has to return back (fluid being plasma) to exchange carbon dioxide and other circulatory functions like carrying waste to kidneys.

So, one more thing. protein is the main determinant for osmotic pressure. Because there is so much large proteins that don't get transported against the thin capillary pores this results in a huge osmotic pressure in which the low solute concentration (interstitium) drives the fluid back into the capillary (high solute concentration)

I hope that makes sense.

Also something really important to remember is that not all the fluid is returned to the capillaries from the interstitium (which is simply surrounding tissue). Hence the importance of the lymphatic system which collects that extra fluid. And what also you should know (something that MCAT likes to test) is that if there is a flaw in excess fluid in tissues (because of faulty protein concentration which would alter the osmotic pressure) than Edema results which is swelling.